Impact of Body Mass Index on Early Postoperative and Long-Term Outcome after Rectal Cancer Surgery.

Background: The aim of this study was to investigate the impact of obesity and underweight onto early postoperative and long-term oncological outcome after surgery for rectal cancer.

Methods: Data from 2008 until 2011 was gathered by a German prospective multicenter observational study. 62 items were reported by the physicians in charge, and a consecutive follow-up was performed if the patient had signed a consent form. Patients were subclassified into: underweight, normal weight, overweight, and obese - using the definitions of the World Health Organization.

Results: In total, 9,920 patients were included, of whom 2.1% were underweight and 19.4% obese. The mean age was 68 years (range 21-99 years). Postoperative morbidity (mean 38.0%) was significantly increased in underweight and obese patients (p < 0.001). In-hospital mortality was 3.1% on average with no significant differences among patient groups (p = 0.176). The 5-year overall survival ranged between 36.9 and 61.3% and was worse in underweight and prolonged in overweight and obese patients compared to those with normal weight (p < 0.001 each). While the 5-year disease-free survival was increased in overweight and obese patients (p < 0.05 each), the 5-year local recurrence rate showed no correlation (p > 0.05 each). Multivariate analysis revealed that advanced age, higher ASA scoring, postoperative morbidity, and advanced tumor growth worsened the long-term survival independently.

Conclusions: Underweight patients had a worse early and long-term outcome after rectal cancer surgery. Overweight and obesity were associated with a significantly better long-term survival.