Obesity is an independent prognostic variable in colon cancer survivors

Abstract

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

Experimental design: BMI (kg/m(2)) was categorized in patients with tumor-node-metastasis stage II and III colon carcinomas (n = 4,381) enrolled in seven randomized trials of 5-fluorouracil-based adjuvant chemotherapy. Cox proportional hazards models were used to determine the association of BMI with disease-free survival (DFS) and overall survival (OS).

Results: Among colon cancer patients, 868 (20%) were obese (BMI, >or=30 kg/m(2)), of which 606 were class 1 (BMI, 30-34 kg/m(2)) and 262 were class 2,3 (BMI, >or=35 kg/m(2)). Obese versus normal-weight patients were more likely to be younger, have distal tumors, show intact DNA mismatch repair, and have more lymph node metastases (P < 0.017). In a multivariate analysis, BMI was significantly associated with both DFS (P = 0.030) and OS (P = 0.0017). Men with class 2,3 obesity showed reduced OS compared with normal-weight men [hazard ratio, 1.35; 95% confidence interval, 1.02-1.79; P = 0.039]. Women with class I obesity had reduced OS [hazard ratio, 1.24; 95% confidence interval, 1.01-1.53; P = 0.045] compared with normal-weight women. Overweight status was associated with improved OS in men (P = 0.006), and underweight women had significantly worse OS (P = 0.019). BMI was not predictive of therapeutic benefit.

Conclusions: Obesity is an independent prognostic variable in colon cancer survivors and shows gender-related differences. These data suggest that obesity-related biological factors can influence clinical outcome.

Fig. 1

Relationship between obesity and clinical outcome for stage II and III colon cancer patients participating in adjuvant chemotherapy trials. A, OS in men only. B, OS in women only.

Fig. 2

A, HRs and 95% CIs for DFS and OS in relation to BMI category in all patients. B, HRs and 95% CIs for OS by BMI category in men versus women. HRs were adjusted for age, stage, treatment, and gender.