Impact of adjuvant chemotherapy using gemcitabine plus S-1 after surgical resection for advanced biliary cancer.

132 Background: The impact of adjuvant chemotherapy for advanced biliary cancer remains controversial. We previously failed to show survival benefit of adjuvant gemcitabine chemotherapy (UMIN000014018). The aim of this study was to evaluate the safety and efficacy of adjuvant gemcitabine plus S-1 chemotherapy after surgical resection for advanced biliary cancer. Methods: Between January 2006 and May 2019, a total of 110 patients who underwent surgical resection for biliary cancer (UICC Stage II or more) were enrolled in this study. Of these, 33 patients subsequently received 12 cycles of adjuvant chemotherapy (GS group), and 77 patients underwent surgery alone (S group). A cycle of chemotherapy consisted of oral S-1 70mg/m2 for 7 consecutive days and intravenous gemcitabine 1000mg/m2 on day 7, followed by a 1-week break from chemotherapy. Clinicopathological factors and patient survival were compared between the two groups. Results: GS group had significantly younger patients ( P = 0.036) and higher UICC T factor ( P = 0.001). Surgical procedure was significantly different in the two groups (P = 0.010). Other patient demographics and tumor characteristics were similar between the two groups. The completion rate of adjuvant chemotherapy was 57.6%, and there was no treatment-related deaths. All grades and grade 3/4 adverse event were seen in 60.6% and 33.3%, respectively. Three-year recurrence-free and overall survival rates were significantly higher in GS group than S group (61.9% vs. 34.4%, P = 0.016; 77.6% vs. 39.7%, P < 0.001, respectively). Conclusions: Adjuvant chemotherapy using gemcitabine plus S-1 was well tolerated and it would be an effective treatment strategy for the patients with resected advanced biliary cancer. Based on these results, randomized controlled study should be warranted.