Body mass index (BMI) as a prognostic and predictive factor in stage II/III colon cancer: An analysis of the ACCENT database.

Abstract

e21126 Background: Obesity is an established risk factor for developing colon cancer. We determined the impact of body mass index (BMI) upon prognosis and treatment benefit using the Adjuvant Colon Cancer Endpoints (ACCENT) database. Methods: BMI (kg/m2) was categorized at baseline in patients (pts) with TNM stage II and III colon carcinomas (n= 23,315) enrolled in 20 randomized trials of 5-fluorouracil-based adjuvant therapy. Cox models were used to determine the association of BMI with time-to-recurrence (TTR), disease-free (DFS) and overall survival (OS). Results: Among colon cancer pts, 4194 (18%) were obese (BMI ≥30 kg/m2), 8347 (35.8%) overweight (BMI 25-29.9 kg/m2), 9062 (38.9%) normal weight (BMI 20-24.9 kg/m2), and 1712 (7.3%) underweight (BMI < 20 kg/m2). Obese vs normal weight pts were more likely to be younger (median age 60 vs 61 yr; p=0.0006), have distal tumors (57% vs 55%; p=0.0066), and be stage III vs II (68% vs 64%; p<0.0001). In univariate analyses, obese [HR 1.13 (1.06, 1.20), p=0.0003] and underweight [HR 1.12 (1.02, 1.23), p=0.0145] pts had poorer OS compared to normal weight pts. Analysis by gender demonstrated that underweight men [HR 1.26 (1.09, 1.47), p=0.0022], but not women (HR=1.09, p=0.13), had a worse OS vs normal weight pts. Similar results were found for DFS and OS; TTR was weaker among underweight pts. BMI category was not predictive of treatment benefit. Conclusions: Obese and underweight colon cancer survivors have a statistically significant, but clinically modest, worse prognosis. Obesity does not predict chemotherapy benefit. Studies to determine if weight loss can attenuate the adverse prognostic impact of obesity are warranted. BMI Category TTR HR (95% CI) 5-yr TTR Rate (95% CI) P-value OS HR (95% CI) 5-yr OS Rate (95% CI) P-value Obese 1.07 (1.01, 1.14) 67.5% (66.0-68.9) 0.0357 1.11 (1.04, 1.18) 72.6% (71.3-74.0) 0.0024 Overweight 1.01 (0.96, 1.06) 69.5% (68.5-70.5) 0.7856 0.99 (0.94, 1.05) 74.5% (73.6-75.5) 0.7141 Normal* 1.0 69.9% (69.0-70.9) NA 1.0 74.9% (74.0-75.8) NA Underweight 1.13 (1.03, 1.24) 67.0% (64.8-69.4) 0.0080 1.22 (1.11, 1.33) 72.6% (70.5-74.8) <0.0001 Adjusted for age, stage, treatment, and gender.*Reference group.