Survival of women with colon cancer in relation to precancer anthropometric characteristics: The Iowa women's health study

Background: We hypothesized that precancer anthropometric variables are associated with mortality among women who developed colon cancer in a prospective cohort, the IowaWomen's Health Study (IWHS). Methods: From 1986 to 2005, 1,096 incident cases of colon cancer were identified (mean age at diagnosis, 73 years). Anthropometric characteristics were self-measured before colon cancer diagnosis (in 1986). Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) for all-cause and colon-cancer mortality, adjusted for age at cancer diagnosis, stage, education, smoking status, and pack-years of smoking. Results: During the follow-up of up to 20 years, 493 women died; 289 had colon cancer as the underlying cause. The HRs of all-cause death were increased for the highest versus lowest tertile for weight (HR, 1.39; 95% CI, 1.10-1.76; P trend = 0.005); waist to hip ratio (WHR; HR, 1.36; 95% CI, 1.08-1.72; P trend = 0.008), and waist (HR, 1.45; 95% CI, 1.15-1.82; P trend = 0.001). Compared with that for body mass index (BMI) of 18.5 to 24.9 kg/m², HRs were increased for BMI ≥30 kg/m² (HR, 1.45; 95% CI, 1.14-1.85) and for the few women with BMI <18.5 kg/m² (HR, 1.89; 95% CI, 1.01-3.53). Colon cancer mortality was positively associated with WHR and waist: HR, 1.37 (95% CI, 1.02;1.85; P trend = 0.04) and 1.34 (95% CI, 1.01-1.80; P trend = 0.05), respectively, for the highest versus lowest tertile. Conclusion: Greater precancer anthropometric measures and BMI <18.5 kg/m² predicted poorer survival among colon cancer patients. Higher abdominal adiposity measured by WHR and waist was associated with increased risk of colon cancer death. Impact: Prediagnostic obesity may be a modifiable risk factor for death in colon cancer patients.