366 Background: Recent improvements in chemotherapy for initially unresectable pancreatic ductal adenocarcinoma (UPDAC) occasionally show remarkable antitumor effect and lead to conversion surgery (CS). However, the optimal indication and clinical impact of CS remains unknown. We have recently developed a new regimen consisted of biweekly S-1, oxaliplatin, and irinotecan (SOXIRI). In this regimen, we used S-1 in alternate-day administration instead of 5-FU, that can be more feasible than FOLFIRINOX. The aim of this study was to evaluate the clinical impact of CS after SOXILI treatment for initially UPDAC. Methods: We conducted an open-label, single-arm, phase II study that was carried out at Nara Medical University and Kansai Medical University in Japan. Patients with untreated metastatic and locally advanced PDAC were enrolled. They received 80 mg/m2 twice a day of S-1 for 2 weeks in alternate-day administration, 150 mg/m2 of irinotecan on day 1, and 85 mg/m2 of oxaliplatin on day 1 of a 2-week cycle. Results: The 35 enrolled patients received a median of six (range: 2-15) treatment cycles. The RR was 22.8%; median OS, 17.7 months; and median PFS, 7.4 months. Major grade 3 or 4 toxicity included neutropenia (54%), anemia (17%), febrile neutropenia (11%), anorexia (9%), diarrhea (9%), and nausea (9%). Twenty-three out of 35 patients of UR-PDAC were unresectable locally advanced pancreatic cancer (UR-LAPA). Seven out of 23 patients with UR-LAPA underwent CS. Distal pancreatectomy with celiac axis resection was performed in three patients, central pancreatectomy was performed in one patient. Pancreatoduodenectomy (PD) was performed in two patients, and PD with portal vein resection in one patient. Two out of seven patients had postoperative complications. One case had grade B pancreatic fistula, and the other case underwent cholecystectomy due to acute cholecystitis. The median OS in patients who received CS was 31.4 months. Conclusions: SOXIRI regimen has shown promising clinical efficacy with acceptable tolerability in patients with unresectable pancreatic cancer. Furthermore, it may be a potent first-line treatment when considering conversion surgery. Clinical trial information: UMIN000014339.
Clinical usefulness of conversion surgery for unresectable pancreatic cancer diagnosed on multidetector computed tomography imaging: Results from a multicenter observational cohort study by the Hokkaido Pancreatic Cancer Study Group (HOPS UR‐01)
