Phase II study of combination chemotherapy with S-1 plus Avastin in unresectable or recurrent colorectal cancer after failure of prior chemotherapy, including irinotecan and oxaliplatin regimens.

Interventions: A phase II study of third-line and subsequent treatment with S-1 alone performed in Korea in patients with unresectable, advanced or recurrent colorectal cancer reported a disease control rate of 42.9% (95% confidence interval, 23.3% to 62.4%). Because bevacizumab was combined with S-1 in the present study, a higher disease control rate is expected. The threshold rate was therefore set at 30% and the expected rate at 50%. Using Fleming’s single-stage procedure, we estimated that 35 patients would be required for the study to have a statistical power (1- ) of 0.80 or higher with a one-sided  value of 0.05. We assumed that more than 10% of enrolled patients would drop out of the study. The target number of enrolled patients was therefore set at 40.
Primary outcome(s): Disease control rate
Study Design: Single arm Non-randomized