Background FOLFOXIRI plus bevacizumab is the first-line treatment for metastatic colorectal cancer (mCRC) but demonstrates high neutropenia incidence among Asian patients. Hence, we conducted the randomized phase II QUATTRO-II study (ClinicalTrials.gov identifier: NCT04097444; Japan Registry of Clinical Trials identifier: jRTCs041190072) to evaluate the safety and efficacy of capecitabine, oxaliplatin, and irinotecan (CAPOXIRI) combination plus bevacizumab versus FOLFOXIRI plus bevacizumab, expecting a lower incidence of neutropenia without compromising the efficacy. Methods We investigated the recommended doses (RD) of oxaliplatin and irinotecan as a safety lead-in portion of Step 1 before initiating the randomized portion as Step 2. Four dose levels of CAPOXIRI (fixed dose of capecitabine, 1600 mg/m2; escalated/de-escalated doses of oxaliplatin and irinotecan) plus bevacizumab (7.5 mg/kg) were investigated in a 3 + 3 manner. A dose level of ≤ 2/6 of dose-limiting toxicity (DLT) cases was expected as the RD. Results In Step 1, we included nine patients (three and six in levels 0 and + 1, respectively). Level 0 (irinotecan, 200 mg/m2; oxaliplatin, 100 mg/m2) did not demonstrate DLTs. In level + 1 (irinotecan, 200 mg/m2; oxaliplatin, 130 mg/m2), although one patient experienced grade 4 febrile neutropenia, no further safety concerns were observed. As a preliminary efficacy result, the objective response rate in all nine patients was 89 % (100 and 83 % in levels 0 and + 1, respectively). Conclusions The RD of CAPOXIRI plus bevacizumab was 200, 130, and 1600 mg/m2 for irinotecan, oxaliplatin, and capecitabine, respectively, and 7.5 mg/kg for bevacizumab. The randomized portion is still ongoing.
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