Body mass index at diagnosis and survival among colon cancer patients enrolled in clinical trials of adjuvant chemotherapy

BACKGROUND: Although obesity is an established risk factor for developing colon cancer, its prognostic impact and relation to patient sex in colon cancer survivors remains unclear. METHODS: The authors examined the prognostic and predictive impact of the body mass index (BMI) in patients with stage II and III colon carcinoma (N = 25,291) within the Adjuvant Colon Cancer Endpoints (ACCENT) database. BMI was measured at enrollment in randomized trials of 5-fluorouracil-based adjuvant chemotherapy. Association of BMI with the time to recurrence (TTR), disease-free survival (DFS), and overall survival (OS) were determined using Cox regression models. Statistical tests were 2-sided. RESULTS: During a median follow-up of 7.8 years, obese and underweight patients had significantly poorer survival compared with overweight and normal-weight patients. In a multivariable analysis, the adverse prognostic impact of BMI was observed among men but not among women (P_interaction =.0129). Men with class 2 and 3 obesity (BMI ≥35.0 kg/m²) had a statistically significant reduction in DFS (hazard ratio [HR], 1.16; 95% confidence interval [CI], 1.01-1.33; P =.0297) compared with normal-weight patients. Underweight patients had a significantly shorter TTR and reduced DFS (HR, 1.18; 95% CI, 1.09-1.28; P <.0001) that was more significant among men (HR, 1.31; 95% CI, 1.15-1.50; P <.0001) than among women (HR, 1.11; 95% CI, 1.01-1.23; P =.0362; P_interaction =.0340). BMI was not predictive of a benefit from adjuvant treatment. CONCLUSIONS: Obesity and underweight status were associated independently with inferior outcomes in patients with colon cancer who received treatment in adjuvant chemotherapy trials.