Abstract A071: Definitive radiation therapy for treatment of non-metastatic pancreatic ductal adenocarcinoma: Practice patterns and outcomes
Authors: Michael M. Caplan, Brian W. Labadie, Hope Choy, Albert Lee, Weijia Fan, David P. Horowitz
Journal: Cancer Research (2024)

Abstract Background: Advances in radiation therapy (RT) have allowed for increased biologically effective doses, or ablative RT, to be safely administered to pancreatic tumors. Pancreatic ductal adenocarcinoma (PDA) is diagnosed as local disease without metastasis in roughly 45% of patients (pts) however only 20-25% of pts are candidates for upfront surgical resection, and many are medically unfit to undergo surgery. In such patients, ablative RT can be given with curative intent, termed definitive RT (dRT). Defining practice patterns and outcomes of dRT is needed. Methods: A retrospective chart review was performed on pts with non-metastatic PDA who underwent dRT, defined as &amp;gt; = 100Gy BED over a protracted hypofractionation course, for treatment at our institution. Data collected included: age, gender, primary tumor location, resectability status, surveillance scan frequency and modality, chemotherapy (chemo) used, site of recurrence, cancer antigen (CA) 19-9 levels pre and post dRT, adverse events, and vital status. Neoadjuvant (NA) and adjuvant chemo was defined as chemo received within 6 weeks prior to dRT and 6 weeks after dRT, respectively. Time from diagnosis and dRT until death (OS and dRT-OS, respectively) and time from diagnosis and dRT until progression (PFS and dRT-PFS, respectively) was calculated. Time from diagnosis and dRT until metastasis (MFS and dRT-MFS, respectively) was also calculated. Results: A total of 25 pts who received dRT were identified. Median dose of RT given was 6750 cGY (range 3750-6750) in 15 fractions. Median age at receipt of dRT was 71.5 years (range 50-91), 50% were female. 76% of pts had pancreatic head mass and 24% of pts were considered resectable at time of diagnosis. 2 patients received dRT after isolated local recurrence after surgical resection. 80% of pts received chemo of any kind prior to dRT and 65% of those patients as NA chemo. 35% of patients received 2 chemo regimens prior to dRT; 55% and 65% of patients received mFOLFIRINOX and gemcitabine-based therapy, respectively. 12% of pts received adjuvant chemo. 43% of patients had at least 1 surveillance PET scan. 80% of patients had progression of any kind; of which 85% and 40% experienced distant and local recurrence, respectively. The median OS and dRT-OS was 17.3 months (95% CI 12.2-NA) and 10.1 months (95% CI 6.5-NA), respectively. The median PFS and dRT-PFS was 14.7 months (95% CI 10.3-17.9) and 5.1 months (95% CI 3.6-9.3), respectively. The median MFS and dRT-MFS was 14.7 months (95% CI 10.3-18.0) and 5.6 months (95% CI 3.6-11.3), respectively. Median CA 19-9 pre dRT was 85 (range 4.3-1790) and post-dRT was 42 (range 1.2-1673). 56% of pts had RT-associated toxicity of any kind. Conclusions: Of a single-institutional cohort of 25 patients with non-metastatic PDA who received dRT, more than half of patients received NA chemo; adjuvant chemo was rarely given. dRT provided high rates of local control while MFS was nearly identical to PFS, emphasizing the importance of systemic therapy to reduce distant recurrence in pancreatic cancer treated with dRT. Citation Format: Michael M. Caplan, Brian W. Labadie, Hope Choy, Albert Lee, Weijia Fan, David P. Horowitz. Definitive radiation therapy for treatment of non-metastatic pancreatic ductal adenocarcinoma: Practice patterns and outcomes [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A071.