Differences in toxicity between men and women treated with 5‐fluorouracil therapy for colorectal carcinoma

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Abstract
BACKGROUND Recent explorations suggest that women may experience more severe 5‐fluorouracil (5‐FU)–related toxicity than men. The patient populations from 4 Southwest Oncology Group colorectal carcinoma trials with 5‐FU–containing regimens were examined for toxicity differences between the genders. METHODS The current study included 1074 patients from 4 trials. Hypotheses regarding differences in specific toxicities were generated via exploratory analyses on the data from the 2 earlier trials (n = 505 patients), using basic univariate techniques and classification tree methods. Validation of these hypotheses was performed on data from the 2 later trials (n = 569 patients) using logistic regression models for dichotomous toxicity outcomes and rank‐sum tests for comparisons of overall toxicity grade. RESULTS 5‐FU toxicity was more extensive in women than in men in terms of average maximum toxicity grade (P = 0.005), number of different types of toxicity experienced (P = 0.009), and incidence of severe toxicities (P = 0.02). The incidence of ≥ Grade 2 hematologic toxicity in the 2 later trials was higher in women than in men and women experienced more frequent moderate to severe mucositis compared with men. CONCLUSIONS Differences in 5‐FU toxicity profiles between men and women were hypothesized after an exploratory analysis, and then verified by an independent confirmatory analysis using data from the 2 later trials. This process provided substantial evidence for gender differences in specific aspects of 5‐FU toxicity that persist across a range of treatment regimens, patient characteristics, and cancer trial settings. Cancer 2005. © 2005 American Cancer Society.