S-1 monotherapy as first-line treatment in patients with advanced biliary tract cancer: a multicenter phase II study

A pilot phase II study showed S-1 monotherapy to be safe and active against biliary tract cancer (BTC). We, therefore, conducted a multicenter phase II study to evaluate the antitumor effect and safety of S-1 in previously untreated patients with advanced BTC. Eligible patients had pathologically proven, unresectable adenocarcinoma with no prior chemotherapy or radiotherapy. Patients received S-1 orally at 80 mg/m² total daily dose divided b.i.d. for 28 days followed by 14 days of rest. Of the 41 enrolled patients, 40 were assessable. The primary tumor sites were as follows: gallbladder (n = 20), extrahepatic bile duct (n = 15), and the ampulla of Vater (n = 5). One patient (2.5%) achieved a complete response, 13 patients (32.5%) had partial responses, 17 patients (42.5%) had no change, 7 patients (17.5%) had progressive disease, and 2 patients (5.0%) were not evaluable. The overall objective response rate was 35.0%. The median overall survival (median OS) was 9.4 months, and the median time to progression was 3.7 months. Grade 3 or 4 toxicities included fatigue (7.5%), anorexia (7.5%) and T-Bil elevation (7.5%). Significant antitumor activity combined with a mild toxicity profile was observed. This monotherapy warrants further evaluation in a randomized study.