Randomized phase II study of S-1 dosing schedule for resected colorectal cancer

Postoperative adjuvant chemotherapy for patients with stage III Colorectal cancer (CRC) is now internationally accepted as standard care for improving patient outcomes. The Adjuvant Chemotherapy Trial of S-1 for Colorectal Cancer (ACTS-CC) confirmed the non-inferiority of S-1 to tegafur/urcail/leucovorin in terms of overall survival and disease-free survival in patients with stage III CRC after curative surgery. However, the 6-month completion rate of S-1 treatment was 76.5% in the ACTS-CC. Therefore, treatment completion remains an unresolved problem.

A randomized phase II trial was designed to evaluate the efficacy and safety of oral daily administration and alternate-day administration of S-1 as adjuvant chemotherapy in curatively resected stage III CRC. Enrolled patients were assigned to either S-1 daily administration (Arm A) or alternate-day S-1 administration (Arm B). Assigned treatment will start within 8 weeks after surgery. In both arms, S-1 dosing (oral) will be based on body surface area (80 mg/day for body surface area<1.25 m2, 100 mg/day for 1.25-1.5 m2, or 60 mg/day for >1.5 m2). In Arm A, S-1 will be administered orally for 28 days, followed by a 14-day rest. Administration will be conducted for 24 weeks from the date of therapy start. In Arm B, S-1 will be administered orally on alternate days for 28 weeks from the date of the start of therapy. After treatment, all patients will be observed without additional therapy unless recurrent lesions or other cancer lesions occur. The primary endpoint is treatment completion rate. Secondary endpoints include 3-year disease-free survival, compliance, and adverse events.

Previously, S-1 alternate-day intake maintained the efficacy of chemotherapy while reducing adverse effects for patients with R0-resected stage II/III gastric cancer. Improvement of chemotherapy completion rate for patients with colorectal cancer will lead to an improved patient prognosis. Therefore, a randomized phase II trial has been designed to examine the efficacy of alternate-day versus current standard daily S-1 administration as adjuvant chemotherapy for R0-resected stage III colorectal cancer.

This study was registered on 18 February 2014 with University Hospital Medical Information Network Clinical Trials Registry: UMIN000013185.