Objectives: Although overweight body mass is an established risk factor for colorectal cancer incidence, few studies have examined the association between body mass index (BMI) and mortality after colorectal cancer diagnosis. We examined survival in a group of postmenopausal women according to BMI.
Methods: Using the Wisconsin Cancer Reporting System we identified and enrolled 633 postmenopausal women aged 38-74 years who were diagnosed with colorectal cancer in 1988-1991. These women were interviewed by telephone; vital status was ascertained via Wisconsin death certificates. Cox proportional hazards regression was used to estimate multivariate risks of colorectal cancer-specific and all-cause mortality.
Results: Both underweight (BMI <20.0 kg/m2) (Hazard Ratio (HR) 2.3, 95% Confidence Interval (CI) 1.0-5.4) and obese (BMI > or = 30.0 kg/m2) women (HR 2.1, 95% CI 1.1-3.8) were at increased risk of colon cancer death, as compared to normal weight women (BMI 20.0-24.9 kg/m2). No association was observed for those with rectal cancer. Approximately 50% increases in all-cause mortality were observed among underweight and obese women with colorectal cancer. Postmenopausal hormone use did not appear to modify these associations.
Conclusions: Underweight and obese postmenopausal women with colon cancer were at increased risk of death, though comorbidities may partially account for this risk.