UGT1A1*28, toxicity and outcome in advanced colorectal cancer: Results from Trial N9741

Abstract

3520 Background: This report examines UGT1A1*28, toxicity, and outcome in trial NCCTG N9741 patients (pts) receiving combination chemotherapy for advanced colorectal cancer. Methods: Blood samples were collected from 520 pts randomized between 2/18/00 and 7/18/02. Pts were treated with irinotecan/5-fluorouracil (5FU)/leucovorin (LV) (IFL, n=114), oxaliplatin/5FU/LV (FOLFOX, n=299), irinotecan/oxaliplatin (IROX, n=107). 19% of IFL pts received full-dose (125 mg/m 2 ) irinotecan; the rest received a reduced dose (100 mg/m 2 ). Toxicity was evaluated every cycle. Correlation of dichotomous outcomes and genotype status used Fisher’s exact tests. Univariate logistic regression was used to test the association between continuous variables and binary outcomes, including a test of trend, and multivariate logistic regression to adjust for known risk factors: performance status, age, gender. Time to progression (TTP) and overall survival (OS) were tested for association with UGT1A1 using the log-rank test. Statistical significance was prospectively set at .01 to control for multiple comparisons. Results: Frequency of UGT1A1 genotype was 44% 6/6, 42% 6/7, and 9% 7/7. In all arms, the rate of grade (G) 4 neutropenia (neut) ( Table ) and G3+ febrile neut (FN) was higher in pts with the 7/7 than in pts with 6/7 and 6/6. No association was seen between UGT1A1 and diarrhea, tumor response, TTP, or OS overall or for any treatment arm. The odds ratios for pts with 7/7 developing G4 neut and G3+ FN compared with pts with 6/6 are shown ( Table ). Statistically significant associations between the 7/7 polymorphism and G4 neut were seen in pts treated with IROX (P=.004) and in all pts (P=.007). The association between 7/7 and G3+ FN was also significant for IROX (P=.006). Conclusions: There is a higher risk of neut in 7/7 pts. Due to low frequency of the 7/7, exclusion of all pts with 7/7 reduces the overall G4 neut rate from 18% to 17%. UGT1A1 was not a predictor of response, TTP, or OS for any arm. [Table: see text] [Table: see text]