Purpose: Obesity is associated with an increased risk of colon cancer. However, the influence of body mass index (BMI) upon the outcome of colon cancer survivors and its relationship to gender remains unknown.

Experimental Design: BMI (kg/m2) was calculated and categorized in patients with TNM stage II and III colon carcinomas (n= 4,381) enrolled in 7 randomized trials of 5‐fluorouracil‐based adjuvant chemotherapy. Cox proportional hazards modeling was used to determine the association of BMI with disease‐free and overall survival.

Results: Among colon cancer patients, 868 (20%) were obese (BMI ≥30 kg/m2) of which 606 were class 1 (BMI 30–34 kg/m2) and 262 were class 2,3 (BMI ≥35 kg/m2). Obese versus normal‐weight patients were more likely to be younger, have distal tumors, show intact DNA mismatch repair (MMR), and have increased lymph node metastases (p <0.017). The association of BMI and MMR status was dependent upon patient age (p= 0.031). In a multivariate analysis, BMI was significantly associated with both disease‐free (p=0.030) and overall survival (p=0.0017). Men with class 2,3 obesity showed reduced overall survival compared to normal weight men [HR 1.35 (1.02, 1.79); p=0.039]. Women with class I obesity had reduced overall survival [HR 1.24 (1.01, 1.53), p=0.045] compared to normal weight women. BMI was not predictive of therapeutic benefit.

Conclusions: Obesity is associated with intact DNA mismatch repair status and was an adverse, independent prognostic variable in colon cancer survivors. Interventions to reduce obesity have the potential to improve patient outcomes in colon cancer survivors.

Citation Information: Cancer Prev Res 2010;3(1 Suppl):B111.

Copyright © January 7, 2010, American Association for Cancer Research
2010