Phase II clinical study of alternate-day oral therapy with S-1 as first-line chemotherapy for locally advanced and metastatic pancreatic cancer

Purpose: Based on the results of first-line chemotherapy for advanced pancreatic cancer, S-1 was confirmed to be non-inferior to gemcitabine. However, the recommended regimen of 4 weeks of administration followed by 2 weeks of drug withdrawal frequently causes adverse effects. On the other hand, we experienced in clinical practice that alternate-day administration of S-1 reduced adverse effects and were tolerable for advanced pancreatic cancer patients unwilling to continue the standard daily administration. We therefore conducted a multicenter cooperative prospective study to compare daily with alternate-day administration of S-1 for advanced pancreatic cancer. Methods: Patients with advanced pancreatic cancer were eligible for enrollment in this trial. S-1 was administered at a dose of 40-60 mg twice daily, calculated according to body surface area, on Monday, Wednesday, Friday, and Sunday. Each treatment cycle was 42 days. The primary end point was overall survival (OS). Secondary end points were safety, response rate (RR), progression-free survival (PFS), and time to treatment failure (TTF). Results: Forty-eight patients were evaluable for response. OS as the primary end point was 8.4 months (95 % CI 5.4-10.8), and the 1-year survival rate was 29.2 %. PFS was 5.5 months, and TTF was 3.9 months. RR was 10.4 %, and the disease control rate was 79.2 %. Grade 3/4 hematological and non-hematological toxicities were minor. All of these adverse reactions were tolerable and reversible. Conclusions: The current data demonstrate the mitigation of adverse effects with alternate-day administration of S-1, and this appears to be a more sustainable option for advanced pancreatic cancer.