Body mass index (BMI) and DNA mismatch repair status in colon cancers from patients treated in adjuvant therapy trials.

10590 Background: Obesity is an established risk factor for developing colon cancer and may be prognostic among survivors. To gain biological insight into obesity-associated tumors, we determined the association of BMI with the DNA mismatch repair (MMR) system. Methods: BMI (kg/m2) was determined and categorized at study enrollment in patients (pts) with TNM stage II and III colon carcinomas (n= 2,700) who participated in 10 randomized trials of 5-fluorouracil-based adjuvant therapy conducted by NCCTG or NSABP. MMR status had been analyzed, and deficient MMR was defined as MSI-H or loss of MLH1, MSH2 and/or MSH6 proteins by IHC. Chi-square and/or logistic regression models were used to determine the association of BMI with MMR status and clinical variables. Results: Deficient MMR (dMMR) was detected in 438 (16%) colon cancers. Among pts, 635 (24%) were obese (BMI >30 kg/m2), 1036 (38%) overweight (BMI 25-29.9 kg/m2), 886 (33%) normal weight ((BMI 20-24.9 kg/m2), and 143 (5%) underweight (BMI < 20 kg/m2). ...