Role of Conversion Surgery for Unresectable Pancreatic Cancer After Long-Term Chemotherapy

Background: Unresectable pancreatic cancer (UR-PC) has a poor prognosis. Although conversion surgery has been considered a promising strategy for improving prognosis in UR-PC, the clinical benefit offered to patients with UR-PC remains controversial. This study aimed to investigate the clinical benefits of conversion surgery in patients with UR-PC. Methods: We evaluated patients with UR-PC referred to our department for possible surgical resection between January 2008 and June 2017. Resectability was evaluated using multimodal imaging in patients who underwent chemotherapy for more than 6 months. Conversion surgery was performed only in patients who were judged eligible for R0 resection. Results: In total, 90 patients were evaluated. Among them, only 22 (24.4%) could actually undergo conversion surgery, and the R0 resection rate was 72.7% (16/22). Although Evans grade ≥ IIB was noted in six patients (27.3%), none achieved complete response (CR). The median survival time was significantly longer among patients who underwent conversion surgery than in the unresected patients who underwent chemotherapy (21.3 months vs. 12.6 months; p < 0.001). Multivariate and Kaplan–Meier analyses revealed microvascular invasion to have a significant adverse effect on recurrence-free survival (RFS: 7 months vs. not reached, p = 0.004) and overall survival (OS: 21 months vs. 85 months, p = 0.047). Conclusions: After long-term chemotherapy, conversion surgery for UR-PC is associated with long-term survival. Microvascular invasion is predictive of poor prognosis in these patients; adjuvant protocols are therefore needed for patients with microvascular invasion.