TS-1 in Combination With Calcium Folinate in Patients With Heavily Pre-treated mCRC

Simon's optimal two-stage design will be used to determine the sample size for this study. • Stage I: \>1/9: The first 9 evaluable patients enrolled, \>1 (or ≥2) responders are required in order to enter the second stage, otherwise the trial will be terminated at the first stage due to futility. • Stage II: Total \>8/34: For the total 34 evaluable patients, \>8 (or ≥9) responders are required to conclude the effectiveness of the study regimen. The primary endpoint will be disease control rate which will be presented in frequency tabulation with two-sided 95% confidence interval (using binomial estimation). The secondary endpoints are described as follows: * ORR will be presented in frequency tabulation with two-sided 95% confidence interval; * TTP will be estimated by Kaplan-Meier method with two-sided 95% confidence interval; * OS will be estimated by Kaplan-Meier method with two-sided 95% confidence interval; * Incidence of adverse events (AEs), serious adverse events (SAEs) \[Safety and Tolerability\] : assessed by CTCAE v4.0. Safety parameters will only be analyzed on the safety analysis set and be presented in frequency tabulation.