Prospective multicenter study to investigate the introduction rate of second-line S-1 in gemcitabine-refractory unresectable pancreatic cancer

Purpose: S-1 is one of the second-line candidate agents for gemcitabine-refractory unresectable pancreatic cancer. Two phase II studies have been reported for second-line chemotherapy with S-1, but these studies did not investigate introduction rate and suitable dose of second-line S-1. Therefore, we conducted a prospective multicenter study in which chemo-naïve patients were enrolled and had two levels of S-1 dose. Methods: Chemo-naïve patients with unresectable pancreatic cancer were enrolled. This study started with 80 mg/m²/day dose of S-1 as second-line chemotherapy and tolerability was checked. When tolerability was not confirmed in initial patients, the dose of S-1 was shifted to 60 mg/m²/day. When tolerability was confirmed at 80 or 60 mg/m²/day, the study continued, and up to 20 patients were accumulated with the dose. In addition, the introduction rate of second-line S-1 was examined. Results: Six of the initial 7 patients with 80 mg/m²/day dose of S-1 completed one course of second-line chemotherapy. Twenty patients were accumulated with an 80 mg/m²/day dose of S-1. With the exception of one patient continued gemcitabine chemotherapy, two of the remaining 19 patients withdrew from this study because of toxicity during the period of gemcitabine chemotherapy. Fifteen of the remaining 17 gemcitabine-refractory patients could complete one course of S-1 as second-line chemotherapy with acceptable toxicity. Conclusions: This prospective multicenter study showed that 15 (78.9%) out of 19 chemo-naïve unresectable pancreatic cancer patients could complete one course of 80 mg/m²/day dose of S-1 as second-line chemotherapy after first-line gemcitabine chemotherapy failure with tolerable toxicity.