Prognostic advantage of irinotecan dose escalation according to uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) genotyping in patients with metastatic colorectal cancer treated with bevacizumab combined with 5-fluorouracil/leucovorin with irinotecan in a first-line setting.

This study compared the clinical responses of patients with metastatic colorectal cancer (mCRC) with 5-fluorouracil/leucovorin with irinotecan (FOLFIRI) plus bevacizumab therapy either with or without uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) genotyping and irinotecan dose escalation. Of 107 total patients with mCRC, 79 were classified as the study group and 28 as the control group. The study group received irinotecan dose escalation based on UGT1A1 genotyping whereas the control group did not. Clinicopathologic features, response rates, and survival were compared for the 2 groups. The clinical response rate of patients with mCRC treated with FOLFIRI plus bevacizumab under UGT1A1 genotyping and irinotecan dose escalation was significantly better than that of those without these prospective tests and dose escalation (P = 0.028). Both progression-free survival (PFS) and overall survival were significantly greater in clinical responders than nonresponders (both, P < 0.001), and PFS was significantly greater among the study group patients than among the control group patients, with a median PFS of 12.2 months vs 9.4 months (P = 0.025). Grade 3/4 adverse events were not significantly different between the 2 groups (P = 0.189). Patients with mCRC undergoing UGT1A1 genotyping may receive escalated doses of irinotecan to obtain a better clinical response/outcome with comparable toxicities.