Prognostic impact of body mass index upon cancer recurrence and survival in stage III colon cancer patients from adjuvant chemotherapy trials

Abstract

11088 Background: Obesity is associated with an increased risk of colon cancer. However, the influence of body mass index (BMI) upon the prognosis of patients with established colon cancer remains unknown. Methods: We conducted a retrospective study of 1,803 patients with surgically resected stage III colon cancer who were enrolled in five randomized trials of 5-fluorouracil-based adjuvant chemotherapy conducted by the North Central Cancer Treatment Group. Patient height and weight were recorded at study entry and BMI (kg/m2) was calculated and categorized. Cancer recurrence or death were monitored during 5 years of follow-up. The score and likelihood ratio p-values were determined from univariate and multivariate Cox regression models respectively, after stratifying by study. Results: Among stage III colon cancer patients, 19% were obese (BMI 30 kg/m2), 37% were overweight (BMI, 25 to 29.9 kg/m2), 38% were of normal-weight (BMI, 20 to 24.9 kg/m2), and 6% were underweight (BMI < 20 kg/m2). Obese versus normal-weight patients showed higher rates of lymph node (LN) metastasis (>3 LNs; 38% vs. 29%, p <0.01) and tumor site was more likely to be distal versus proximal (52% vs. 45%, p= 0.03). No differences in age, gender, or histologic grade were found. In a univariate analysis, obese patients had significantly worse disease-free survival (DFS) compared with normal-weight patients (hazard ratio 1.25 (95% CI: 1.04 -1.51; p= 0.02). The 5 year DFS rates were 49% in obese patients versus 57% in normal weight subjects. Furthermore, poorer DFS was observed for obese patients after adjusting for age, sex, histologic grade, and tumor site (p= 0.03). Neither overweight nor underweight patients (vs. normal-weight) had significantly different DFS. Analysis of the predictive impact of BMI for 5-FU-based adjuvant therapy is in progress. Conclusions: Obesity (BMI 30 kg/m2) was associated with a greater number of metastatic lymph nodes and poorer disease-free survival in patients with stage III colon cancer, suggesting that obesity influences tumor progression. No significant financial relationships to disclose.