Phase I study of TAS-102 and irinotecan combination therapy in Japanese patients with advanced colorectal cancer

Background TAS-102 is a nucleoside antitumor agent consisting of trifluridine (FTD) and tipiracil hydrochloride (TPI). We investigated the recommended dose (RD) of TAS-102 plus irinotecan for metastatic colorectal cancer refractory to 5-fluorouracil (5-FU) and oxaliplatin. Methods This study was used a escalated dose of TAS-102 (40–70 mg/m(2)/day, for 5 days a week with 2 days rest for 2 weeks, followed by a 14-day rest) with a fixed dose of irinotecan (150 mg/m(2) on Days 1 and 15 of a 28-day schedule). The primary endpoints were determination of RD and assessment of safety. Results Ten patients were enrolled; 7 at the Level 1 (50 mg/m(2)/day) and 3 at the Level 2 (60 mg/m(2)/day). One patient at Level 1 was excluded from the analysis of dose-limiting toxicities (DLT) and efficacy. Five DLTs occurred in 3 patients; 1 patient at Level 1 (Grade 3 febrile neutropenia and Grade 4 neutropenia), and 2 patients at Level 2 (Grade 3 febrile neutropenia in two patients and Grade 4 neutropenia in one). Grade 3 or higher treatment-related adverse events were neutropenia (100 %), leukopenia (70 %), febrile neutropenia (30 %) and lymphopenia, anaemia (20 % each). 2 patients (22 %) achieved partial response with the duration of response were 112 and 799 days. Conclusion The RD was determined to be 50 mg/m(2)/day of TAS-102 combined with 150 mg/m(2) of irinotecan although further investigation to explore optimal regimen is warranted.