The combination of a cancer vaccine, pembrolizumab, and stereotactic body radiation in patients with locally advanced pancreatic cancer: a single-arm, phase II study

Domain: chemistry
Published: 2026-03-18
Editorial outcome: minor_revision

Abstract
In this Phase II study (NCT02648282) of locally advanced pancreatic cancer (LAPC), 58 patients were enrolled and intended for an immunotherapy including GM-CSF-secreting allogeneic pancreatic cancer vaccine (GVAX) and pembrolizumab and stereotactic body radiation therapy (SBRT) following standard chemotherapy. Fifty-four evaluable patients received two cycles of immunotherapy and SBRT and reassessed for resectability. After resection or biopsy, patients received continued immunotherapy for two years. At a median follow-up of 19.6 months, the median distant metastasis free survival (DMFS), the primary endpoint, for all evaluable patients was 9.8 months. Secondary endpoint analysis shows that, of these, 35 patients (64.8%) were deemed potentially resectable, and 24 underwent R0/R1 resections. Resected patients had a majority of R0 resections (91.7%). The overall resection rate was 44.4%. Patients who underwent resection had a median DMFS of 20.3 months. Median overall survival (OS), a secondary endpoint, for all evaluable patients from the start of the immunotherapy was 21.8 months, with resected patients reaching 29.7 months and unresected patients at 12.1 months. From diagnosis, median OS was 28.2 months, with resected patients achieving 36.7 months, while unresected patients had 19.7 months. In conclusion, the combination of GVAX, pembrolizumab, and SBRT showed promising efficacy in LAPC patients with favorable survival outcomes, especially those who underwent R0/R1 resections. However, patients with unresectable disease still maintained significantly worse DMFS and OS. The regimen demonstrated a manageable safety profile.

Introduction
The prognosis for pancreatic ductal adenocarcinoma (PDAC) is dismal and the overall 5-year survival rate for all stages at diagnosis is around 12% in the United States1. The management of PDACs requires a multidisciplinary approach that integrates multiple treatment modalities, including surgery, radiotherapy (RT), chemotherapy, and, in the clinical trial settings, emerging therapies such as immunotherapy and targeted therapy. Pancreatectomy offers the only chance of cure for pancreatic cancer. Based on the severity of the blood vessel involvement, localized pancreatic cancers are categorized into resectable pancreatic cancer, borderline resectable pancreatic cancer, and locally advanced pancreatic cancer (LAPC). Given the aggressive nature of pancreatic cancer and the complexity of its treatment, a multimodality strategy, with neoadjuvant chemotherapy, is essential to address the disease at different stages for an improved overall survival (OS) and, with neoadjuvant RT to further increase the chance of R0 resection. We previously reported that 20% of LAPCs treated with chemotherapy followed by stereotactic body radiation therapy (SBRT) were successfully down-staged and underwent R0 or R1 resection2.

About 30% of the newly diagnosed PDAC cases first present as LAPC3, which is deemed surgically inoperable because of the involvement of the surrounding vasculature. The current standard treatment for LAPC is a combination of induction chemotherapy and RT including chemoradiation or SBRT4. Compared to conventional chemoradiation, SBRT resulted in more frequent complete pathologic responses5 and reduced lymphocyte suppression in LAPCs6. Nevertheless, novel therapeutic strategies are still highly demanded to increase surgical resection rates and ultimately curability in LAPCs.

For many advanced malignancies, immunotherapies, particularly the immune checkpoint inhibitors (ICIs), have become an alternative or additive standard of care treatment. Unfortunately, immunotherapy has demonstrated minimal therapeutic effects in PDACs7. ICIs such as anti-PD-1 or PD-L1 antibodies potentiate tumor antigen-specific effector T cells (Teffs) by reinvigorating their function. The quantity of tumor-infiltrating Teffs predicts the survival outcome in those cancer types that respond to immunotherapy, but is low in the tumor microenvironment (TME) of PDACs8. The TME in PDAC is also immunosuppressive, not only preventing T cell infiltration, but also suppressing Teff function9.

Recent studies have suggested that RT can prime the TME with Teffs by inducing immunogenic tumor cell death which triggers innate immune responses, thus serving as an “in situ vaccination"10,11. Such a priming process may enhance the effectiveness of immunotherapies such as ICIs. Preclinical and clinical studies demonstrated that immune responses to RT and ICIs are synergized to improve antitumor activities in various tumor types, including melanoma and non-small cell lung cancer12. Multiple studies in preclinical mouse models of PDAC demonstrated that RT can enhance antitumor response to PD-1 or PD-L1 blockade or dual CTLA-4 and PD-1 blockade, and abscopal effects of RCT were observed in these studies13-15. In a phase I clinical trial of patients with metastatic PDAC, SBRT to target lesions in combination with anti-PD-L1 antibody durvalumab or in combination with durvalumab plus anti-CTLA4 antibody tremelimumab showed a moderate therapeutic benefit and an acceptable safety profile with an objective response rate of 5.1%16. In a single-arm phase II clinical trial, RT combined with anti-CTLA4 antibody ipilimumab and anti-PD-1 antibody nivolumab in 25 metastatic, microsatellite-stable PDAC patients resulted in a disease control rate of 20% and objective response rate of 12%17. By far, the largest phase II CheckPAC trial randomized metastatic PDAC patients to receive SBRT to target lesions in combination with nivolumab or with both ipilimumab and nivolumab demonstrated a higher objective response rate (14.0% vs. 2.4%) in the dual ICI arm than single ICI arm18. However, as RT is not standard of care for metastatic PDACs and not all the metastatic lesions are candidates for SBRT, the comparable benefit and feasibility of RT in combination of ICIs to systemic therapies remain unknown and would be difficult to assess.

However, RT is still considered to be a standard of care for LAPC, and thus represents an appealing indication to pursue for RT in combination with ICIs. However, prior phase II studies do not show the benefit of anti-PD-1 antibody pembrolizumab being added to RT for borderline resectable PDACs19 and our preclinical data suggest that anti-PD-1 antibody in combination with RT alone would not be sufficient to induce Teffs14. RT can lead to an in situ cancer vaccination effect, which, however, may be associated with inadequate tumor antigen release, insufficient antigen presentation, and immunosuppressive TME. Recent advances in cancer vaccine focus on mRNA-based platforms20 and delivery technologies such as lipid nanoparticles, hydrogels, scaffolds and polymeric nanoparticles21. They show promise in clinical trials for both immunologically "hot" and "cold" tumors including PDAC, particularly when administered in a minimal disease setting to prevent the recurrence22-24. Combination strategies to improve the efficacy of cancer vaccines include ICIs, cytokines, and chemotherapy25.

We have previously demonstrated that a granulocyte-macrophage colony-stimulating factor-secreting allogenic PDAC vaccine (GVAX) administered as a neoadjuvant therapy induced a robust tumor infiltration of Teffs and other immune cells, which formed tertiary lymphoid aggregates26-28. Addition of anti-PD-1 antibody to GVAX27,28 as neoadjuvant therapy for resectable PDACs decreased the quantity of PD-1+CD8+ and PD-1+CD4+ T-cells, supporting the presence of therapeutic effect of anti-PD-1 antibody. Therefore, we developed a single-center, single-arm, phase II clinical trial J15237 (NCT02648282) to test the combination of GVAX, anti-PD-1 antibody pembrolizumab, and SBRT following induction chemotherapy for LAPC patients29. We first reported the correlative studies of this clinical trial, showing that this radioimmunotherapy combination drives TME to feature several antitumor immune response characteristics, including enhanced Teffs infiltration, that are associated with longer survival30. Moreover, we found that adding SBRT to the combination of anti-PD-1 antibody and GVAX shortens the distances from PD-1+CD8+ T cells to tumor cells and to PD-L1+ myeloid cells30.

Here, we provide the first comprehensive report on the safety and efficacy data of this clinical trial. The data showed that the combination of immunotherapy and RT for stage III PDAC is safe and, comparing to the historical control cohort, significantly prolongs the distant metastasis free survival (DMFS) among the surgically explored patients or surgically resected patients.

Results
Demographics and Clinicopathologic Characteristics
From July 18th, 2016, to December 14th, 2020, 58 patients with LAPC and who met the eligibility criteria were enrolled to the study (Figure 1, Figure 2). Of the enrolled patients, 54 were considered evaluable for disease response after receiving two cycles of the combination treatment of cyclophosphamide, GVAX and pembrolizumab, SBRT and had one follow-up scan. These patients had a mean age of 64.2 years old (range: 42.0 - 84.0) and 46.3% were female (Table 1). The majority of patients (88.9%) had a poorly or moderately differentiated adenocarcinoma. Of the 54 evaluable subjects, 35 subjects (64.8%) were deemed to have potentially resectable PDAC following two cycles of study treatments and subsequently underwent explorative laparotomy (Table 2), including 24 subjects who underwent R0/R1 resections (44.4% of total evaluable subjects) and 11 subjects who were explored and found unresectable. Out of the 11 explored, but unresected patients, 8 had peritoneal carcinomatosis and 3 had locally advanced unresectable diseases (Table 2). There was no difference in the rate of resectability whether induction chemotherapy was FOLFIRINOX or Gemcitabine/nab-paclitaxel.

Of the 24 patients who underwent R0/R1 resections (Table 3), a majority had R0 resections (91.7%) and no regional nodal involvement (70.8%) while their pT stages (0, 1, 2, 3, 4) were approximately equally distributed (8.3%, 25%, 25%, 16.7%, 25%, respectively), All tumors had low tumor mutation burdens (median 1.55/Mb [range 0.42– 2.67]).

Efficacy
At the median follow up time of 19.6 months (mo), median DMFS from first immunotherapy was 9.8 mo (95% CI: 6.3, 19.4) (Figure 3a) and that of surgically explored patients was 10.2 mo (95% CI: 7.4, 26.3) (Figure 3b). Median DMFS among those patients who underwent R0/R1 resection was 20.3 mo (95% CI:10.2, NA) (Figure 3c). In contrast, those who were explored, but did not undergo resection due to presence of peritoneal disease or persistent locally advanced unresectable disease had a median DMFS of 2.4 mo (95% CI:2.4, NA) (Figure 3d). However, two patients with persistent locally advanced unresectable diseases had a DMFS >20 months.

Median OS from the starting date of the immunotherapy among 54 evaluable patients was 21.8 mo (95% CI:13.6, 29.7) (Figure 4a) and that of surgically explored patients was 27.9 mo (95% CI:17.3, 59.8) (Figure 4b). Among the patients who underwent R0/R1 resection, median OS of 29.7 mo (95% CI:23.1, NA) (Figure 4c). In contrast, those surgically explored, but who did not undergo resection had a median OS of 12.1 mo (95% CI:10.9, NA) (Figure 4d). Median time from the start of immunotherapy to surgical exploration was 75.5 days (95% CI: 71.0, 86.0); and that from the end of immunotherapy to surgical exploration was 53.0 days (95% CI, 50.0, 63.0). Thus, there was no significant delay in surgical exploration due to immunotherapy. Median time from the demonstration of metastasis till death was 5.06 mo (95% CI:3.35, 8.47) in the entire J15237 cohort, 3.63 mo (95% CI: 0.92, 12.32) in the resected cohort, and 6.03 mo (95% CI: 3.91, 9.60) in the unresected cohort, suggesting that once patients developed metastasis, the survival time would be short regardless of the resection status.

Median OS from the time of initial diagnosis among 54 evaluable patients was 28.2 mo (95% CI:20.4, 36.7) (Figure 4e) and that of surgically explored patients was 35.6 mo (95% CI:25, NA) (Figure 4f). Among those surgically explored, the patients who underwent R0/R1 resection had a median OS of 36.7 mo (95% CI:28.8, NA) (Figure 4g). In contrast, those surgically explored, but who did not undergo resection had a median OS of 19.7 mo (95% CI:17.2, NA) (Figure 4h). The difference between median OS from the time of initial diagnosis and that from the starting date of the immunotherapy reflects the length of induction chemotherapy, which appears to be similar among different subgroups of patients according to resectability.

Safety
All patients experienced mild reactions (Grade 1 -2) at the vaccine injection site. Grade 3-4 treatment-related adverse events primarily involved immune related adverse events occurred in 12% of patients, including pneumonitis (n=1), diabetic ketoacidosis from immune related pancreatitis (n=1), abdominal pain and colitis (n=1), elevated liver enzymes (n=2), nephritis (n=1), and rash (n=1) (Table 4). Elevated liver enzymes were not associated with clinical evidence of hepatitis. No delay of surgery due to treatment-related adverse events or unexpected postoperative complications were noted. Among patients eligible for surgical resection, one died of cholangitis prior to surgery, unrelated to study treatments.

Comparison between the J15237 cohort and the historical control cohort
To address the effect of neoadjuvant immunotherapy, J15237 patients were also compared to a historical control cohort of LAPC patients from the Johns Hopkins Pancreatic Cancer Registry during the time when J15237 was enrolling, 68 patients with LAPC were identified using the same eligibility criteria as J15237. Of these 68 patients, 45 were deemed to have potentially explorable PDAC following the neoadjuvant chemotherapy and SBRT and subsequently underwent explorative laparotomy. These 45 surgically explored historical control patients had a mean age of 65.3 years old (range: 48.7 – 79.0) and 44.4% were female (Supplemental Table 1). During laparotomies, 42 subjects underwent R0/R1 resections. Of the 42 patients who underwent R0/R1 resections, 81.0% had R0 resections; 38.1%, 28.6%, 21.4% and 11.9% had pT-stage 1, 2, 3, or 4 diseases, respectively; and 59.5% had no regional nodal involvement (Supplemental Table 2). Common variables between the J15237 and historical control cohorts are comparable (Supplemental Table 3, Supplemental Table 4). DMFS and OS were obtained from the explored historical control cohort of 45 patients due to lack of consistent followup on those patients who did not undergo surgical exploration.

The DMFS among the surgically explored patients in the J15237 clinical trial was significantly longer than that in the historical control cohort (median DMFS 10.2 vs. 9.5 mo, p<0.001) (Figure 3b) with an HR of 0.34 (95% CI: 0.19, 0.61; Table 5), stratified by resectability. The DMFS among the resected patients in the J15237 clinical trial was significantly longer than that in the historical control cohort (median DMFS 20.3 vs. 10.2 mo, p=0.002) (Figure 3c) with an HR of 0.40 (95% CI: 0.22, 0.72; Table 5).

The OS from the starting date of immunotherapy and that from the date of initial diagnosis among the surgically explored patients in the J15237 clinical trial was not significantly different, but demonstrates a trend of improvement, compared to that from the starting date of SBRT and that from the date of initial diagnosis in the historical control cohort (median OS 27.9 vs. 26.0 mo, p=0.338 and 35.6 vs. 33.1 mo, p=0.426, respectively) (Figure 4b,f) with an HR of 0.77 (95% CI:0.45, 1.32, p=0.340) and an HR of 0.80 (95% CI:0.47, 1.38, p=0.427), respectively, stratified by resectability (Table 5). The OS from the starting date of immunotherapy and that from the date of initial diagnosis among the resected patients in the J15237 clinical trial was similarly not significantly different, but demonstrates a trend of improvement, compared to that from the starting date of SBRT and that from the date of initial diagnosis in the historical control cohort (median OS 29.7 vs. 26.1 mo, p=0.2 and 36.7 vs. 34.1 mo, p=0.284, respectively) (Figure 4c,4g) with an HR of 0.68 (95% CI:0.37, 1.23, p= 0.203) and an HR of 0.72 (95% CI:0.39 ,1.32, p=0.286), respectively (Table 5).

Methods
Ethics and Compliance
The study (J15237) was approved by the Johns Hopkins Institutional Review Board and Institutional Biosafety Committee, as well as the Food and Drug Administration Center for Biologics Evaluation and Research and the National Institutes of Health Recombinant DNA Advisory Committee (NCT02648282). The trial was conducted according to the Declaration of Helsinki and the Good Clinical Practice guidelines of the International Conference of Harmonization. Informed, written consent was obtained from all patients.

Study Design
This is a single-center, single-arm, phase II clinical trial of patients with LAPC seen at the Johns Hopkins Hospital (Baltimore, Maryland, USA). Eligible patients with LAPC received treatments of GVAX administered intradermally in combination with immunomodulatory doses of cyclophosphamide and anti-PD-1 antibody (pembrolizumab), and SBRT prior to the surgical evaluation (Figure 1). If participants were deemed potentially surgical candidates, surgical exploration would be performed. Regardless of whether tumors were resected, participants without metastatic disease would further receive the standard of care chemotherapy for two 4-week cycles followed by the maintenance therapy with every 3 week cycles of cyclophosphamide, GVAX, and pembrolizumab. Further information regarding the trial design can be found in clinicaltrials.gov.

Study Population and Evaluable Patients
The target population for this study was patients with LAPC. Key eligibility requirements at time of enrollment included the following: age above 18 years old; confirmed diagnosis of PDAC; deemed to have a locally advanced tumors by multidisciplinary tumor board review of the radiographic studies at the time of initial diagnosis according to the National Comprehensive Cancer Network guideline; who remained without metastatic disease after receiving at least 4-four week cycles, but no more than 8-four week cycles of FOLFIRINOX or gemcitabine/nab-paclitaxel based chemotherapy; no known secondary malignancies within five years of diagnosis of pancreatic cancer; Eastern Cooperative Oncology Group performance status ≤1; no radiographic evidence of metastases; no serious autoimmune disease requiring treatment with systemic corticosteroids; adequate organ function. All patients who met trial criteria were offered the trial without any anticipated bias. As pre-planned in the clinical protocol, patients evaluable for efficacy endpoints were those who received at least the first two cycles of GVAX and pembrolizumab in combination with a full course of SBRT. All subjects who received the first dose of study therapy were evaluable for safety endpoints.

Outcomes/Endpoints
The primary endpoint was DMFS. A sample size of 54 evaluable subjects provided 80% power to detect an increase in the median DMFS from 7.7 months based on historical data to 13.6 months (corresponding to a HR of 0.57), using one-sample test with two-sided type I error of 0.05. Secondary endpoints included the clinical endpoints of OS, subsequent surgical resectability, pathologic response. Quality of life was assessed via EORTC QLQ-C30/Pan26 (v3.0) questionnaire and will be presented in another study. As described above, exploratory correlative studies were also conducted and published elsewhere30.

Enrollment
From July 18th, 2016, to December 14th, 2020, 58 patients were enrolled. The data reported herein reflect follow up through June 1st, 2022.

Treatment Schema and Assessments
Participants underwent baseline biopsies at time of fiducial placement for SBRT. Study treatments were given on 21-day cycle, with cyclophosphamide 200mg/m2 IV and pembrolizumab 200 mg IV administered on Day 1 and GVAX intradermally injected equally into six intradermal areas in both lower limbs and the non-dominant upper limb, as described previously administered on day 2. Linac based SBRT were given as previously described33 with 5 fractions of 6.6 Gy from Days 1 to 5 of cycle 2 (Figure 1). After two cycles, clinical resectability was determined by consensus of multidisciplinary team. Tumors deemed resectable proceeded for surgical exploration. If tumors remained clinically unresectable, participants underwent repeat biopsy. After resection or biopsy, all patients without metastatic disease received another two 4-week cycles of either FOLFIRINOX or gemcitabine/Nab-paclitaxel-based treatments at the discretion of their primary oncologists. Following these post-SBRT chemotherapy, participants who remained metastasis-free would continue to receive every 21-day cycle of cyclophosphamide, GVAX, and pembrolizumab for 1 year, followed by maintenance nine cycles of pembrolizumab every three weeks with concurrent every six-month cyclophosphamide/GVAX for four doses if response/tolerance persisted (Figure 1).

Patients were assessed for local or distal disease recurrence by CT scans prior to enrollment, following recovery from definitive surgery, and then every 3 cycles while on study treatment. Toxicities were graded using CTCAE v.4.0. Postoperative complications within 30 days of surgery were graded by the Clavien Dindo Criteria.

Statistical Analysis
DMFS was defined as time from the start of immunotherapy until identification of distant metastases on imaging. Individuals were censored with respect to DMFS at the date of last restaging scan if they were alive and had no evidence of metastatic disease. For patients who died within 3 months of the last scan showing no recurrence, date of death would be counted as an event date of DMFS. OS was defined as the time from the start of immunotherapy until death of any causes. Additional OS from the time of initial diagnoses until death of any cause was also calculated. Individuals were censored with respect to OS at the date of last known alive. Kaplan-Meier method was used to summarize DMFS and OS.

Historical Control Cohort Generation and Analysis
This study was initially designed to compare with the historical phase 2 multi-institutional trial evaluating gemcitabine and SBRT as neoadjuvant therapy for LAPCs34; however, since the clinical trial initiation, the neoadjuvant chemotherapy has changed utilizing more intensive cytotoxic therapy (FOLFIRINOX and gemcitabine/nab-paclitaxel compared to gemcitabine) for longer time periods (4-8 months pre-RT, compared to historical < 6 months). Therefore, for comparison, a historical control cohort was generated, consisting of 45 patients who received definitive pancreatic cancer resection from June 2013 to May 2019 at Johns Hopkins Hospital/Sidney Kimmel Cancer Center. The data cutoff used for the historical control cohort analysis is December 31, 2021. Eligibility criteria for the historical control cohort were the same as the trial: patients with LAPC who received neoadjuvant chemotherapy with either mFOLFIRINOX or Gemcitabine/nab-paclitaxel followed by SBRT at least 4 months later (Supplemental Figure 1). The comparisons of patient characteristics and resectability between J15237 cohort and historical control cohort were conducted using Mann-Whitney U tests for continuous variables and Fisher’ exact tests for binary variables. Stratified log-rank tests, stratified by resectability, were performed for DMFS and OS to compare J15237 vs. historical control cohorts, and difference was quantified by hazard ratio estimate from Cox regression stratified by resectability. According to available data, there is no obvious difference in the time from the diagnosis to the initiation of chemotherapy between the J15237 cohort and the historical control cohort. Among the surgically explored patients, we compared the OS from the starting date of immunotherapy in the J15237 trial to that from the starting date of SBRT in the historical control cohort, as well as the OS since the date of initial diagnosis between them. Subgroup comparisons were performed by resected and un-resected patients, for surgically explored patients. Tests were two-sided and p-values less than 0.05 were considered to indicate statistical significance.

Data Availability
Disaggregated data at individual patient level (Supplementary Dataset 1 for J15237 cohort and Supplementary Dataset 2 for historical control cohort) and source data for Figures and Tables are provided. Study protocol is available within the Supplementary Information file. All data are available within the Article, Supplementary Information or Source Data file. Additional details of the trial, data, contact information, proposal forms, and review and approval process are available at the following website: https://clinicaltrials.gov/study/NCT02648282.

Code Availability
No custom code is used. The analysis used standard functions in the software. Study data were recorded using Microsoft Excel (2016) and Microsoft Access (2016) and stored on a HIPAA complaint drive. Statistical analyses were performed using R (version 4.2.1) and Prism (version 9.3.1). Figures were composed using R and Microsoft PowerPoint (2016).

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The manuscript entitled “The combination of a cancer vaccine, pembrolizumab, and stereotactic body radiation in patients with locally advanced pancreas cancer: a single-arm, phase II study” presents findings from a phase II clinical trial investigating a novel multimodal therapeutic strategy for patients with LAPC. This study evaluates the safety, feasibility, and preliminary efficacy of a combination regimen comprising GVAX, the immune checkpoint inhibitor pembrolizumab, and SBRT. By integrating immunotherapy with precision-targeted radiation, the study explores a promising avenue for enhancing antitumor immune responses in an otherwise treatment-refractory disease. The trial’s innovative design and translational potential make it a valuable contribution to the ongoing search for effective therapies in pancreatic cancer. Overall, this manuscript is well-structured and thorough, with high-quality figures. Thus, I recommend accepting the paper after the authors successfully address the following comments.\nMajor comments:\n1. For the title, replace “pancreas cancer” with “pancreatic cancer,” which is the more accurate and widely used terminology.\n2. In the introduction section, include a brief overview of current surgical strategies for pancreatic cancer, especially R0 and R1 resections.\n3. Some ongoing or completed clinical trials are mentioned in the introduction. To improve clarity and readability, it is recommended to include a table summarizing these trials along with other relevant studies, indicating their design, endpoints, and key findings.\n4. Please include a brief introduction to cancer vaccines. To reflect the latest progress in the field, cite recent relevant literature, such as PMID: 37783860, PMID: 38848720, PMID: 39662677, PMID: 38951662, and PMID: 39048489.\n5. Abbreviations should be defined only at their first mention. Please check the manuscript carefully to ensure consistency and avoid redundant definitions. In addition, as numerous abbreviations were used throughout the body text and diagrams, please add a complete list of abbreviations to ensure the clarity of this paper.\n6. In the “Safety” section, please list the common grade 1–2 adverse events along with their incidence rates.\n7. It is recommended to include a discussion on the limitations of the methodology of this study.\n8. Include a section or paragraph discussing future research directions and the potential clinical implications of this combination therapy.\nOther minor comments:\n1. Line 123: Revise “result in in” to remove the redundant “in.”\n2. Line 160: Change “after received two cycles of” to “after receiving two cycles of.”\n3. Line 156: Revise “Thus, there was not a significant delay in surgical exploration due to immunotherapy” to “Thus, there was no significant delay in surgical exploration due to immunotherapy.”\n4. Line 402-404: Add a period at the end of the sentence.", "reviewer_2": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts.", "reviewer_3": "The combination of a cancer vaccine, pembrolizumab, and stereotactic body radiation in patients with locally advanced pancreas cancer: a single-arm, phase II study. Lee et Al.\nIn this study the authors investigate the treatment potential of a neo-adjuvant combination therapy comprising GM-CSF-secreting allogeneic pancreatic cancer vaccine (GVAX), cyclophosphamide, pembrolizumab, and SBRT following standard chemotherapy in patients with LAPC. Two cycles were administered prior to assessment of resectability with the possibility of continued treatment for up to two years.\nSome translational analyses from the trial were published in 2024. In the present manuscript the authors report on primary and secondary endpoints comprising efficacy and toxicity. For comparison of efficacy data, the authors have established a local historical control group for comparison.\nSeveral subgroup analyses were performed and while the overall DMFS did not seem to differ from previously reported PFS from a prior trial the main finding was a DMFS of 20.3 mo in the resectable subgroup of patients.\nComments\nUnfortunately, no translational analyses are included in the manuscript. Given the hypothesis driven multi-combination treatment strategy and the different efficacy outcome in patient subgroups it appears of outmost importance to search for immune parameters associated with treatment outcome. Thus, it would have strengthened the manuscript significantly to include the tumor and blood immune assessments defined as correlative study endpoints in the protocol.\nReference 7 on progress in immunotherapy for pancreatic cancer is from 2016 it should be possible to find a more recent one.\nPage 7, line 147-152; it is not reasonable to state that the trial rational was based on translational data from the trial.\nPage 7, line 160; please add cyclophosphamide to the text\nEfficacy section; it is recommended to move interpretation text and comparison with previous trial data (line 187-188, 192-194, and 212-215) to the discussion section. In any case, it should be clear that CI is taken into consideration when claiming favorable outcome.\nPage 9, line 201; consider exchanging ‘development of metastasis’ with ‘demonstration of metastasis’\nSafety section; In the ASCO 2021 abstract (https://ascopubs.org/doi/10.1200/JCO.2021.39.15_suppl.4134 ) one death from cholangitis is mentioned why is this not included in the safety reporting ?\nPage 10, line 224 is elevated liver enzymes caused by irhepatitis ?\nPage 10, line 225-226; Were any patients delayed in pembro dosing or skipping of 2nd dose ?\nComparison between the J15237 cohort and the historical control cohort; Please be consistent in the use of the term ‘historical’ in text and figures.\nIn the discussion, page 12, line 290-301 it is not entirely clear for the reader if all the mentioned immune assessment are performed on material from the present trial.\nPage 13, line 308-311; the statement lacks substantiation.\nFigure 3 and 4; please add short heading to the subfigures to indicate subgroups results.", "reviewer_4": "This is an original research article presenting the results of a single-arm, single-institution, open label, phase II study of GVAX vaccine, pembrolizumab, and SBRT in patients with locally advanced pancreatic ductal adenocarcinoma following induction chemotherapy. The primary endpoint of distant metastasis free survival was not reached. The investigators seek to compare the results to a historical control arm from the same institution of similar patients during the same time frame. The survival for patients who underwent resection is impressive.\n1. On line 290, DMSF should be DFMS.\n2. There should be a thorough description of the baseline resectability of all patients. Were borderline resectable patients included? There seems to be high rate of conversion to resectable for truly locally advanced patients. A description of baseline vascular involvement and reasons for unresectability would clarify this.\n3. In patients who became resectable, were they still unresectable following the pre-trial chemotherapy or did they only convert to resectable after neoadjuvant GVAX/pembro/SBRT? Did patients become resectable after chemotherapy alone?\n4. I would be careful of using a post-hoc historical control arm in this somewhat heterogeneous patient population."}, "author_response": "Response to Reviewers\nAs you will see from the reports copied below, the reviewers raise important concerns.\nWe find that these concerns limit the strength of the study, and therefore we ask you to\naddress them with additional work. Without substantial revisions, we will be unlikely\nto send the paper back to review. In particular, As you will see from the reports copied\nbelow, the reviewers raise important concerns. Whilst we would expect you to respond\nto all of the reviewers' comments, in our editorial opinion, comments regarding\nincomplete safety reporting (Reviewer #1, 2, 3), relevance of using historical control\narm (Reviewer #3,4), exclusion immune-assessment correlative study endpoints\n(Reviewer #3), and the inclusion of additional baseline patient resectability details\n(Reviewer #4), are important points to address. This is not to say that we consider any\nof the other comments of the referees less important and would expect you to address\nthem in full. Please highlight all changes in the manuscript text file.\nResponse: Thank you for giving us the opportunity of revising our manuscript and\naddressing reviewers’ comments. All the comments are very helpful. We have\nconducted additional studies and believe our revised manuscript has significantly\nimproved.\nRegarding incomplete safety reporting, we have revised the table 4 and listed the\ncommon grade 1-2 adverse events along with their incidence rates (Reviewer #1). We\nalso added the safety reporting for death “Among patients eligible for surgical resection,\n1 died of cholangitis prior to surgery” (Reviewer #2,3), and explained elevated liver\nenzymes was not associated with clinical evidence of hepatitis (Reviewer #2,3).\nRegarding relevance of using historical control arm, we have gone through the\nmanuscript, and are consistent in the use of the term “historical control cohort”\n(Reviewer #3), and explained the inclusion criteria of historical control cohort\n(Reviewer #4). We have described our already published translational analyses of\nimmune-assessment correlative study endpoints in the Discussion (Reviewer #3).\nPatients deemed to have a locally advanced tumors by multidisciplinary tumor board\nreview of the radiographic studies at the time of initial diagnosis according to the\nNCCN guideline were enrolled. No BRPCs were enrolled. Key eligibility requirements\nat time of enrollment also included who remained without metastatic disease after\nreceiving at least four 4-week cycles, but no more than eight 4-week cycles of\nFOLFIRINOX or gemcitabine/nab-paclitaxel-based chemotherapy. We believe that\nexcluding patients with metastasis after chemotherapy might be the reason for the high\nconversion rate of LAPC in our clinical study (Reviewer #4).\nReviewer #1 (Remarks to the Author):\nThe manuscript entitled “The combination of a cancer vaccine, pembrolizumab, and\nstereotactic body radiation in patients with locally advanced pancreas cancer: a single-\narm, phase II study” presents findings from a phase II clinical trial investigating a novel\nmultimodal therapeutic strategy for patients with LAPC. This study evaluates the safety,\nfeasibility, and preliminary efficacy of a combination regimen comprising GVAX, the\nimmune checkpoint inhibitor pembrolizumab, and SBRT. By integrating\nimmunotherapy with precision-targeted radiation, the study explores a promising\navenue for enhancing antitumor immune responses in an otherwise treatment-refractory\ndisease. The trial’s innovative design and translational potential make it a valuable\ncontribution to the ongoing search for effective therapies in pancreatic cancer. Overall,\nthis manuscript is well-structured and thorough, with high-quality figures. Thus, I\nrecommend accepting the paper after the authors successfully address the following\ncomments.\nResponse: We appreciate that Reviewer 1 considers our study is valuable. We thank\nReviewer 1 for the constructive recommendations. We do believe our manuscript has\nbeen significantly improved by following these recommendations.\nMajor comments:\n1. For the title, replace “pancreas cancer” with “pancreatic cancer,” which is the\nmore accurate and widely used terminology.\nResponse: Thank you for pointing out this typo. We have corrected it.\n2. In the introduction section, include a brief overview of current surgical strategies for\npancreatic cancer, especially R0 and R1 resections.\nResponse: We agree with this reviewer, and have added a new paragraph as below:\nThe management of PDACs requires a multidisciplinary approach that integrates\nmultiple treatment modalities, including surgery, radiotherapy (RT), chemotherapy, and,\nin the clinical trial settings, emerging therapies such as immunotherapy and targeted\ntherapy. Pancreatectomy offers the only chance of cure for pancreatic cancer. Based on\nthe severity of the blood vessel involvement, localized pancreatic cancers are\ncategorized into resectable pancreatic cancer, borderline resectable pancreatic cancer,\nand locally advanced pancreatic cancer (LAPC). Given the aggressive nature of\npancreatic cancer and the complexity of its treatment, a multimodality strategy, with\nneoadjuvant chemotherapy, is essential to address the disease at different stages for an\nimproved overall survival (OS) and, with neoadjuvant RT to further increase the chance\nof R0 resection. We previously reported that 20% of LAPCs treated with chemotherapy\nfollowed by stereotactic body radiation therapy (SBRT) were successfully down-staged\nand underwent R0 or R1 resection (PMID:29596120).\n3. Some ongoing or completed clinical trials are mentioned in the introduction. To\nimprove clarity and readability, it is recommended to include a table summarizing these\ntrials along with other relevant studies, indicating their design, endpoints, and key\nfindings.\nResponse: We thank Reviewer 1 for this constructive recommendation, and have added\na new table (Supplemental Table 5) as below.\nTable S5 Summary of Relevant PDAC Studies in the Literature.\n4. Please include a brief introduction to cancer vaccines. To reflect the latest progress\nin the field, cite recent relevant literature, such as PMID: 37783860, PMID: 38848720,\nPMID: 39662677, PMID: 38951662, and PMID: 39048489.\nResponse: We thank Reviewer 1 for this constructive recommendation, and have added\na new paragraph as below:\nRT can lead to an in situ cancer vaccination effect, which, however, may be\nassociated with inadequate tumor antigen release, insufficient antigen presentation, and\nimmunosuppressive TME. Recent advances in cancer vaccine focus on mRNA-based\nplatforms (PMID 37783860) and delivery technologies such as lipid nanoparticles,\nhydrogels, scaffolds and polymeric nanoparticles (PMID 38951662). They show\npromise in clinical trials for both immunologically \"hot\" and \"cold\" tumors including\nPDAC, particularly when administered in a minimal disease setting to prevent the\nrecurrence (PMIDs 38848720, 39662677, 37165196). Combination strategies to\nimprove the efficacy of cancer vaccines include ICIs, cytokines, and chemotherapy\n(PMID 39048489).\n5. Abbreviations should be defined only at their first mention. Please check the\nmanuscript carefully to ensure consistency and avoid redundant definitions. In addition,\nas numerous abbreviations were used throughout the body text and diagrams, please\nadd a complete list of abbreviations to ensure the clarity of this paper.\nResponse: Thanks, we have checked the manuscript carefully, and added a list of\nabbreviations.\nList of abbreviations\nPDAC pancreatic ductal adenocarcinoma\nRT radiotherapy\nLAPC locally advanced pancreatic cancer\nOS overall survival\nSBRT stereotactic body radiation therapy\nICI immune checkpoint inhibitor\nTeffs effector T cells\nTME tumor microenvironment\nDMFS distant metastasis-free survival\nTAM tumor-associated macrophage\n6. In the “Safety” section, please list the common grade 1–2 adverse events along\nwith their incidence rates.\nResponse: We have listed the common grade 1–2 adverse events along with their\nincidence rates.\nTable 4 Summary of study treatment-related adverse events (N = 58)\nTypes of Adverse Events Grade 1 Grade 2 Grade 3 Any grade Attribution\nEndocrine\nDiabetic Ketoacidosis 0 0 1(2%) 1(2%) Pembrolizumab\nHyperthyroidism 1(2%) 0 0 1(2%) Pembrolizumab\nHypothyroidism 1(2%) 4(7%) 0 5(9%) Pembrolizumab or SBRT\nGastrointestinal\nColitis 0 1(2%) 1(2%) 2(3%) Pembrolizumab\nDry mouth 1(2%) 0 0 1(2%) Pembrolizumab\nNausea 2(3%) 0 0 2(3%) Pembrolizumab\nOral pain 0 1(2%) 0 1(2%) Pembrolizumab\nGeneral\nFatigue 0 1(2%) 0 1(2%) Pembrolizumab\nFever 3(5%) 0 0 3(5%) Pembrolizumab or GVAX\nFlu-like symptoms 2(3%) 1(2%) 0 3(5%) Pembrolizumab or GVAX\nMalaise 4(7%) 0 0 4(7%) Pembrolizumab or GVAX\nChills 2(3%) 0 0 2(3%) Pembrolizumab or GVAX\nLaboratory\nAbnormal LFTs (elevated bilirubin) 0 0 1(2%)\nPembrolizumab\nAbnormal LFTs (normal bilirubin) 0 0 1(2%) 1(2%)\nPembrolizumab\nPancytopenia 0 1(2%) 1(2%) 1(2%)\nPembrolizumab\nArthritis 1(2%) 1(2%) 0 2(3%) Pembrolizumab\nLower Extremity Muscle weakness 1(2%) 0 0 1(2%) GVAX\nMyalgia 4(7%) 0 0 4(7%) GVAX\nRenal and urinary\nNephritis 0 0 1(2%) 1(2%) Pembrolizumab\nUrethritis 0 1(2%) 0 1(2%) Pembrolizumab\nRespiratory\nPneumonitis 0 0\nPembrolizumab\n1(2%) 1(2%)\nSkin\nDermatitis 0 1(2%) 0 1(2%) Pembrolizumab\nDry skin 0 1(2%) 0 1(2%) GVAX\nPruritus 3(5%) 0 0 3(5%) Pembrolizumab or GVAX\nRash 5(9%) 1(2%) 1(2%) 7(12%) Pembrolizumab or GVAX\nUrticaria 1(2%) 0 0 1(2%) Pembrolizumab\n7. It is recommended to include a discussion on the limitations of the methodology of\nthis study.\nResponse: We thank Reviewer 1 for this constructive recommendation. We have\nexpanded the discussion of limitations as below.\nThis study has a few limitations. This study did not use the trend of CA19-9 as a\nsurrogate maker for tumor responses to the study treatment although we collected the\nresults before and after Cycle 1 of immunotherapy. We do not anticipate the change\nof CA19-9 before and after Cycle 1 of immunotherapy would correlate with the\ntreatment response to radioimmunotherapy because of the short interval between two\ntests and because of rising CA19-9 secondary to radioimmunotherapy-induced\ninflammatory reaction. Another limitation of this single arm trial is the potential for\npatient selection bias, as it enrolled patients who remained locally advanced after 4-8\nmonths of chemotherapy or have responded to chemotherapy, thus, were pre-selected\nrather than those newly diagnosed with LAPC. To mitigate the potential impact of\npatient selection bias on treatment effect assessment, we compared the outcomes of the\nJ15237 cohort with a historical control cohort who met the same eligibility criteria as\nthe J15237 trial with matched patient characteristics and also received neoadjuvant\nchemotherapy with either mFOLFIRINOX or Gemcitabine/nab-paclitaxel for a\nminimum of 4 months and a maximum of 8 months followed by SBRT. Although the\ndifference in OS between the J15237 cohort and the historical control cohort does not\nreach statistical significance, there is a numerical improvement in OS particularly\namong the resected patients in the J15237 cohort. Future evaluations of DMFS and\nOS on those who undergo surgical resection is warranted through conducting a\nrandomized study with a larger sample size. Nevertheless, the treatment strategy\nwould need to be further improved to enhance the resectability of LAPCs and the\nresponse of unresected tumors to the treatment. In the future studies for LAPC, the\nradioimmunotherapy strategy shall include macrophage-targeting agents as above\nproposed.\n8. Include a section or paragraph discussing future research directions and the potential\nclinical implications of this combination therapy.\nResponse: We have included a paragraph discussing future research directions and the\npotential clinical implications:\nBased on these findings, we had developed and recently completed a clinical trial of\na CCR2/CCR5 dual antagonist that targets TAMs in combination with nivolumab with\nor without GVAX following mFOLFIRINOX-based induction chemotherapy and\nSBRT for LAPCs (NCT03767582). The endpoints of this new clinical trial are still\nbeing analyzed.\nOther minor comments:\n1. Line 123: Revise “result in in” to remove the redundant “in.”\nResponse: Thank you for pointing out this typo. We have corrected it.\n2. Line 160: Change “after received two cycles of” to “after receiving two cycles\nof.”\nResponse: Thank you for pointing out this typo. We have corrected it.\n3. Line 156: Revise “Thus, there was not a significant delay in surgical exploration\ndue to immunotherapy” to “Thus, there was no significant delay in surgical\nexploration due to immunotherapy.”\nResponse: Thank you for pointing out this typo. We have corrected it.\n4. Line 402-404: Add a period at the end of the sentence.\nResponse: Thank you for pointing out this typo. We have corrected it.\nReviewer #2 (Remarks to the Author):\nI co-reviewed this manuscript with one of the reviewers who provided the listed reports.\nThis is part of the Nature Communications initiative to facilitate training in peer review\nand to provide appropriate recognition for Early Career Researchers who co-review\nmanuscripts.\nResponse: Thank for your review and the constructive recommendations.\nReviewer #3 (Remarks to the Author):\nThe combination of a cancer vaccine, pembrolizumab, and stereotactic body radiation\nin patients with locally advanced pancreas cancer: a single-arm, phase II study. Lee et\nAl.\nIn this study the authors investigate the treatment potential of a neo-adjuvant\ncombination therapy comprising GM-CSF-secreting allogeneic pancreatic cancer\nvaccine (GVAX), cyclophosphamide, pembrolizumab, and SBRT following standard\nchemotherapy in patients with LAPC. Two cycles were administered prior to\nassessment of resectability with the possibility of continued treatment for up to two\nyears.\nSome translational analyses from the trial were published in 2024. In the present\nmanuscript the authors report on primary and secondary endpoints comprising efficacy\nand toxicity. For comparison of efficacy data, the authors have established a local\nhistorical control group for comparison.\nSeveral subgroup analyses were performed and while the overall DMFS did not seem\nto differ from previously reported PFS from a prior trial the main finding was a DMFS\nof 20.3 mo in the resectable subgroup of patients.\nResponse: We appreciate that Reviewer 3 considers our study is valuable. We thank\nReviewer 3 for the constructive recommendations. We do believe our manuscript has\nbeen significantly improved by following these recommendations.\nComments\nUnfortunately, no translational analyses are included in the manuscript. Given the\nhypothesis driven multi-combination treatment strategy and the different efficacy\noutcome in patient subgroups it appears of outmost importance to search for immune\nparameters associated with treatment outcome. Thus, it would have strengthened the\nmanuscript significantly to include the tumor and blood immune assessments defined\nas correlative study endpoints in the protocol.\nResponse: We thank Reviewer 3 for this constructive recommendation and have\ndescribed our separately published translational analyses in the Discussion.\nThe efficacy result presented in this study is consistent with our recently published\ncorrelative studies of this clinical trial23 showing that a positive correlation between\nthe infiltration of GZMB+CD8+ cytotoxic effector T cells and OS in patients who\nunderwent surgical resection was not observed in patients still with unresectable\ndiseases after the study treatment, suggesting that GVAX/pembrolizumab-induced\neffector T cell infiltration did not transform into an improved clinical outcome in\nunresected PDACs. In contrast, a decrease in the M1/M2-like tumor-associated\nmacrophages (TAM) ratio, due to an increase of M2-like TAMs, was significantly\nassociated with OS < 2 years in unresected PDACs. Therefore, M2-like TAMs in\nPDACs that remained unresected following neoadjuvant treatments may account for\nthe lack of benefit from the combination of GVAX and pembrolizumab. Targeting TAM\nmay improve the resectability of LAPCs and/or may improve the outcome of LAPCs\nthat remain unresectable following neoadjuvant treatments. Based on these findings,\nwe recently completed a clinical trial of a CCR2/CCR5 dual antagonist that targets\nTAMs in combination with nivolumab with or without GVAX following\nmFOLFIRINOX-based induction chemotherapy and SBRT for LAPCs\n(NCT03767582). The endpoints of this new clinical trial are still being analyzed.\nReference 7 on progress in immunotherapy for pancreatic cancer is from 2016 it should\nbe possible to find a more recent one.\nResponse: We have updated Reference 7 to the 2024 version as below: Wang J, et al.\nConsensus, debate, and prospective on pancreatic cancer treatments. J Hematol Oncol\n17, 92 (2024) doi: 10.1186/s13045-024-01613-x. PMID: 39390609; PMCID:\nPMC11468220.\nPage 7, line 147-152; it is not reasonable to state that the trial rational was based on\ntranslational data from the trial.\nResponse: We agree with this reviewer. We re-organized the Introduction.\nPage 7, line 160; please add cyclophosphamide to the text\nResponse: Thank you for pointing out this typo. We have corrected it.\nEfficacy section; it is recommended to move interpretation text and comparison with\nprevious trial data (line 187-188, 192-194, and 212-215) to the discussion section. In\nany case, it should be clear that CI is taken into consideration when claiming favorable\noutcome.\nResponse: We have moved interpretation text and comparison with previous trial data\nto discussion section.\nPage 9, line 201; consider exchanging ‘ development of metastasis ’ with\n‘demonstration of metastasis’Safety section; In the ASCO 2021 abstract (https:\n//ascopubs.org/doi/10.1200/JCO.2021.39.15_suppl.4134 ) one death from cholangitis\nis mentioned why is this not included in the safety reporting ?\nResponse: Thank you for pointing out this typo. We have replaced “development of\nmetastasis” by “demonstration of metastasis”. In the Safety section, we have added\n“Among patients eligible for surgical resection, one died of cholangitis prior to surgery,\nunrelated to study treatments.”\nPage 10, line 224 is elevated liver enzymes caused by irhepatitis ?\nResponse: Elevated liver enzymes were not associated with clinical evidence of\nhepatitis.\nPage 10, line 225-226; Were any patients delayed in pembro dosing or skipping of 2nd\ndose ?\nResponse: No patients delayed in pembro dosing or skipping of 2nd dose.\nComparison between the J15237 cohort and the historical control cohort; Please be\nconsistent in the use of the term ‘historical’ in text and figures.\nResponse: Thanks, we have gone through the manuscript, and are consistent in the use\nof the term “historical control cohort”.\nIn the discussion, page 12, line 290-301 it is not entirely clear for the reader if all the\nmentioned immune assessment are performed on material from the present trial.\nResponse: Yes, all the mentioned immune assessment are performed on material from\nthe present trial. We have added references after each result.\nPage 13, line 308-311; the statement lacks substantiation.\nResponse: We now revised the statement as below:\nOur results suggested that the systemic anti-tumor effect from the combination of\nGVAX/pembrolizumab/SBRT would provide more benefits to those with minimal\nresidual disease and prevent the development of distant metastases while the\ncombination is not more effective than SBRT itself on the primary tumors. Thus, the\nfuture development should focus on further improving the resectability of LAPCs.\nFigure 3 and 4; please add short heading to the subfigures to indicate subgroups results.\nResponse: Thank you for this comment. We agree with the Reviewer. We have\nmodified Figure 3 and 4 as below:\nFigure 3 DMFS in the J15237 and historical control cohorts\na. Kaplan-Meier curve among evaluable patients in the J15237 cohort (n=54). b.\nKaplan-Meier curve among surgically explored patients in the J15237 cohort (n=35)\nand historical control cohort (n=45). c. Kaplan-Meier curve among the surgically\nresected patients in the J15237 cohort (n=24) and historical control cohort (n=42). d.\nKaplan-Meier curve among the surgically explored but unresected patients in the\nJ15237 cohort (n=11) and historical control cohort (n=3). The date of death would be\nconsidered a DMFS event for patients who died within three months of the last scan\nindicating there had been no recurrence.\nFigure 4 OS from starting date of study treatment and from initial date of\ndiagnosis in the J15237cohort and that from the starting date of SBRT in the\nhistorical control cohort\na. Kaplan-Meier curve among the evaluable patients in the J15237 cohort (n=54). b.\nKaplan-Meier curve among the surgically explored patients in the J15237 cohort (n=35)\nand in the historical control cohort (n=45). c. Kaplan-Meier curve among the surgically\nresected patients in the J15237 cohort (n=24) and in the historical control cohort (n=42).\nd. Kaplan-Meier curve among the surgically explored but unresected in the J15237\n(n=11) and historical control cohorts (n=3). e. Kaplan-Meier curve among the\nevaluable patients in the J15237 cohort (n=54). f. Kaplan-Meier curve among the\nsurgically explored patients in the J15237 cohort (n=35) and the historical control\ncohort (n=45). g. Kaplan-Meier curve among the surgically resected in the J15237\ncohort (n=24) and the historical control cohort (n=42). h. Kaplan-Meier curve among\nthe surgically explored but unresected in the J15237 cohort (n=11) and historical control\ncohort (n=3).\nReviewer #4 (Remarks to the Author):\nThis is an original research article presenting the results of a single-arm, single-\ninstitution, open label, phase II study of GVAX vaccine, pembrolizumab, and SBRT in\npatients with locally advanced pancreatic ductal adenocarcinoma following induction\nchemotherapy. The primary endpoint of distant metastasis free survival was not reached.\nThe investigators seek to compare the results to a historical control arm from the same\ninstitution of similar patients during the same time frame. The survival for patients who\nunderwent resection is impressive.\nResponse: We appreciate the enthusiasm of Reviewer 4 with our study. We thank\nReviewer 4 for pointing out the issues below and have addressed them in the revised\nmanuscript.\n1. On line 290, DMSF should be DFMS.\nResponse: Thank you for pointing out this typo. We have corrected it.\n2. There should be a thorough description of the baseline resectability of all patients.\nWere borderline resectable patients included? There seems to be high rate of conversion\nto resectable for truly locally advanced patients. A description of baseline vascular\ninvolvement and reasons for unresectability would clarify this.\nResponse: Patients deemed to have a locally advanced tumors by multidisciplinary\ntumor board review of the radiographic studies at the time of initial diagnosis according\nto the NCCN guideline were enrolled. No BRPCs were enrolled. Key eligibility\nrequirements at time of enrollment also included who remained without metastatic\ndisease after receiving 4-8 four-week cycles of FOLFIRINOX or gemcitabine/nab-\npaclitaxel based chemotherapy. We believe that excluding patients with metastasis after\nchemotherapy might be the reason for the high conversion rate of LAPC in our clinical\nstudy.\n3. In patients who became resectable, were they still unresectable following the pre-\ntrial chemotherapy or did they only convert to resectable after neoadjuvant\nGVAX/pembro/SBRT? Did patients become resectable after chemotherapy alone?\nResponse: Due to the very short interval between radioimmunotherapy and surgery, we\ndo not anticipate a change of resectability reflected by a radiographic change following\nradioimmunotherapy. In addition, it is known that response of borderline resectable and\nlocally advanced pancreatic cancer to neoadjuvant therapy is not reflected by\nradiographic indicators (PMID 22605518; PMID: 25755849).\n4. I would be careful of using a post-hoc historical control arm in this somewhat\nheterogeneous patient population.\nResponse: We agree with Reviewer 4 on this important point. This study was initially\ndesigned to compare with the historical data of the phase 2 multi-institutional trial\nevaluating gemcitabine and SBRT as neoadjuvant therapy for LAPCs (PMID:\n25538019); however, since the trial initiation, the neoadjuvant chemotherapy has\nchanged utilizing more intensive cytotoxic therapy (FOLFIRINOX and\ngemcitabine/nab-paclitaxel compared to gemcitabine) for longer time periods (4-8\nmonths pre-RT, compared to historical < 6 months). Therefore, to facilitate appropriate\noutcome assessment of the trial against suitable benchmark data, a historical control\ncohort was generated, consisting of 45 patients who received definitive pancreatic\ncancer resection from June 2013 to May 2019 at Johns Hopkins Hospital/Sidney\nKimmel Cancer Center. The data cutoff used for the historical control cohort analysis\nis December 31, 2021. Eligibility criteria for the historical control cohort were the same\nas the trial: patients with LAPC who received neoadjuvant chemotherapy with either\nmFOLFIRINOX or Gemcitabine/nab-paclitaxel followed by SBRT at least 4 months\nlater (Figure S1). According to available data, there is no obvious difference in the time\nfrom the diagnosis to the initiation of chemotherapy between the J15237 cohort and the\nhistorical control cohort. Patient characteristics of the J15237 and historical control\ncohorts are comparable (Supplemental Table 3, Supplemental Table 4). We have added\na discussion of the limitations of the study, according to Reviewers’ suggestion."}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have thoroughly addressed all reviewer comments in a point-by-point manner and revised the manuscript accordingly.\nI appreciate their effort in improving the quality of the work.\nI believe that the current version of the manuscript is suitable for publication in Nature Communications.", "reviewer_2": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts.", "reviewer_3": "I have no further comments to the revised manuscript where my previous comments have been addressed", "reviewer_4": "The authors have responded adequately to my previous comments and I have no further issues with the manuscript."}, "author_response": "Answer: We appreciate the responses from the four reviewers."}]

Decision letter