Objective: This study investigated the correlations between the different phenotypes of the uridine diphosphate glucuronyl transferase (UGT) 1A1 gene and the treatment of advanced colorectal cancer after the FOLFIRI regimen. Materials and Methods: A total of 240 advanced colorectal cancer patients with stage IV colon cancer or recurrence after radical surgery between January 2014 and December 2018 were included in a retrospective study. All participants were treated with the FOLFIRI regimen until the disease progressed or an intolerable level of toxicity occurred. Results: In this study, three phenotypes of the UGT1A1 gene promoter were found: the homozygous wild type (TA6/6 type, 78.3%), the heterozygous mutant type (TA6/7 type, 19.6%), and the homozygous mutant type (TA7/7 type, 2.1%). Compared with TA6/7 and TA6/6, the risk of nonresponse to FOLFIRI chemotherapy increased by 16%, but the difference was not significant. The risk of death increased by 24%, and there was no significant difference. There was a risk of hematologic and nonhematologic adverse reactions occurring in TA6/7 and TA6/6, and the total risk of adverse reactions increased by 9.3773 times among patients with more than two metastatic organs. Compared with patients with TA6/6, the risk of toxic side-effects increased by 42.8066 times (p = 0.0259) for patients with TA6/7. Among patients who received FOLFIRI chemotherapy for more than four cycles, the proportion with TA6/7 was greater than that with TA6/6. Compared with those with TA6/6, patients with TA6/7 showed a higher risk of hematologic toxicity (22.3246 times, p = 0.0035). Conclusion: The TA6/7 in patients with advanced colorectal cancer had more than two metastatic organs, and received FOLFIRI chemotherapy for more than four cycles compared with TA6/6 patients. Furthermore, the risk of hematologic and nonhematologic adverse reactions significantly increased, and the risk of digestive-tract and hematologic toxicity was more significant.
Keywords: advanced colorectal cancer; clinical prognosis; gene phenotypes; therapy.