Underweight status predicts a poor prognosis in elderly patients with colorectal cancer.

The aim of the present study was to evaluate the effect of underweight status on the survival of elderly patients undergoing surgery for colorectal cancer (CRC). A total of 113 patients aged ≥75 years who underwent curative surgery for CRC were included. In addition to standard perioperative variables, body mass index (BMI) was assessed. The patients were categorized as underweight (BMI<18.5 kg/m2) or non-underweight (BMI≥18.5 kg/m2). The 3-year overall survival (OS) and cancer-specific survival (CSS) were analyzed. Of the 113 patients, 24 (21%) were underweight. The two groups were well-balanced regarding all factors evaluated. In the multivariate analysis, underweight status was an independent indicator of lower 3-year OS [hazard ratio (HR)=2.65; 95% confidence interval (CI): 1.08-6.50; P=0.033] and CSS (HR=3.51, 95% CI: 1.16-10.60; P=0.025) rates. Compared with the non-underweight group, the underweight group had significantly worse 3-year OS (66.7 vs. 86.5%, respectively; P=0.017) and CSS (74.1 vs. 90.9%, respectively; P=0.025) rates. Therefore, underweight status was a significant risk factor for poor survival in elderly CRC patients. The development of effective nutritional interventions may improve the prognosis of such patients.