Clinical Benefits of Conversion Surgery for Unresectable Pancreatic Ductal Adenocarcinoma: A Single-Institution, Retrospective Analysis

Simple Summary Pancreatic ductal adenocarcinoma (PDAC) is a dismal disorder, but conversion surgery (CS) has provided possibilities of better prognosis for unresectable (UR-)PDAC. We retrospectively investigated the clinical benefits of CS in patients with UR-PDAC. We performed CS in 20 of the 398 UR-PDAC cases between 2006 and 2019(5.1%). Compared the overall survival (OS) period among patients undergoing CS, resectable (R), borderline resectable (BR), unresectable locally advanced cancer (UR-LA), and unresectable cancer with distant metastasis (UR-M) groups, the CS group had significantly better survival than R, BR, UR-LA, and UR-M groups (73.7, 32.7, 22.7, 15.7, and 8.8 months, respectively). Moreover, multivariate analysis revealed the presence of chemoraiotherapy and partial response/complete response in the Response Evaluation Criteria in Solid Tumors (RECIST) were statistically significant prognostic factors for OS among patients undergoing CS (p = 0.004 and 0.03, respectively). This study highlights importance of multidisciplinary treatment including CS for patients with UR-PDAC. Abstract Background: Unresectable pancreatic ductal adenocarcinoma (UR-PDAC) has a poor prognosis. Conversion surgery is considered a promising strategy for improving the prognosis of UR-PDAC. This study aimed to investigate the clinical benefits of conversion surgery in patients with UR-PDAC. Methods: We retrospectively evaluated patients with PDAC who were referred to our department for possible surgical resection between January 2006 and December 2019. Conversion surgery was performed only in patients with UR-PDAC who could expect R0 resection. We analyzed the prognostic factors for overall survival among patients who underwent conversion surgery. Results: Overall, 638 patients with advanced pancreatic cancer were enrolled in this study. According to resectability, resectable cancer (R) was present in 180 patients, borderline resectable cancer (BR) was present in 60 patients, unresectable locally advanced cancer (UR-LA) was present in 252 patients, and unresectable cancer with distant metastasis (UR-M) was present in 146 patients. Conversion surgery was performed in 20 of the 398 UR cases (5.1%). The median period between the initial therapy and conversion surgery was 15.5 months. According to the Response Evaluation Criteria in Solid Tumors (RECIST) evaluation, the treatment response was CR in one patient, PR in 13, SD in five, and PD in one. Downstaging was pathologically determined in all cases. According to the Evans grading system, grade I was observed in four patients (20%), grade IIb was observed in seven (35%), III was observed in seven (35%), and IV was observed in two (10%). We compared the overall survival period from initial treatment among patients undergoing conversion surgery; the median overall survival durations in the conversion surgery, R, BR, UR-LA, and UR-M groups were 73.7, 32.7, 22.7, 15.7, and 8.8 months, respectively. Multivariate analysis revealed that the presence or absence of chemoradiotherapy (CRT) and the RECIST partial response (PR)/complete response (CR) for the main tumor were statistically significant prognostic factors for overall survival among patients undergoing conversion surgery (p = 0.004 and 0.03, respectively). Conclusion: In UR-PDAC, it is important to perform multidisciplinary treatment, including CRT with conversion surgery.