While irinotecan ( CPT-11 ) plus cisplatin ( CDDP ) combination therapy and CPT-11 monotherapy have been explored in the second-line setting , the superiority of second-line platinum-based therapies for AGC patients initially treated with S-1 monotherapy has not yet been evaluated ; therefore , we aimed to examine the survival benefit of CPT-11 / CDDP combination over CPT-11 monotherapy .