Randomized phase III study of gemcitabine, cisplatin plus S-1 versus gemcitabine, cisplatin for advanced biliary tract cancer (KHBO1401-MITSUBA)

Background Gemcitabine/cisplatin (GC) combination therapy has been the standard palliative chemotherapy for patients with advanced biliary tract cancer (BTC). No randomized clinical trials have been able to demonstrate the survival benefit over GC during the past decade. In our previous phase II trial, adding S-1 to GC (GCS) showed promising efficacy and we aimed to determine whether GCS could improve overall survival compared with GC for patients with advanced BTC. Methods We performed a mulitcenter, randomized phase III trial across 39 centers. Enrolled patients were randomly allocated (1:1) to either the GCS or GC arm. The GCS regimen comprised gemcitabine (1000 mg/m(2)) and cisplatin (25 mg/m(2)) infusion on day 1 and 80 mg/m(2) of S-1 on days 1-7 every 2 weeks. The primary endpoint was overall survival (OS) and the secondary endpoints were progression-free survival (PFS), response rate (RR), and adverse events (AEs). This study is registered with Clinical trial identification: NCT02182778. Results Between July 2014 and February 2016, 246 patients were enrolled. The median OS and 1-year OS rate were 13.5 months and 59.4% in the GCS arm and 12.6 months and 53.7% in the GC arm, respectively (hazard ratio [HR] 0.79, 90% confidence interval [CI]: 0.628-0.996; P = .046 [stratified log-rank test]). Median PFS was 7.4 months in the GCS arm and 5.5 months in the GC arm (HR 0.75, 95% CI: 0.577-0.970; P = .015). RR was 41.5% in the GCS arm and 15.0% in the GC arm. Grade 3 or worse AEs did not show significant differences between the two arms. Conclusions GCS is the first regimen which demonstrated survival benefits as well as higher RR over GC in a randomized phase III trial and could be the new first-line standard chemotherapy for advanced BTC. To exploit the advantage of its high RR, GCS is now tested in the neoadjuvant setting in a randomized phase III trial for potentially resectable BTC.