RESUMEN
PURPOSE: It is well known that an increased body mass index (BMI) is associated with cancer development. Results from studies on colorectal cancer (CRC) treatment outcome and BMI are however conflicting. Our hypothesis was that a high as well as a low BMI will have negative effects on short-term outcome after CRC surgery. METHODS: Data from the Swedish Colorectal Cancer Registry from 2007 to 2012 was analyzed. A total of 24,587 patients operated on for CRC were included in the study and divided into one of five categories for BMI. Operative bleeding, operating time, surgical complications, and 30-day mortality were compared between groups. RESULTS: Operative bleeding as well as operating time was significantly increased when comparing normal-weight patients to overweight (p < 0.001). 15.1% of normal-weight patients suffered from postoperative surgical complications. This was significantly increased with each BMI step but did not affect the 30-day mortality. However, underweight patients, on the other hand, had fewer complications (13.3%) but an increased 30-day mortality. CONCLUSION: Longer operating times and increased perioperative bleeding may be explanatory factors behind increased postoperative complication rates for CRC patients with higher BMI. In underweight patients, advanced disease may be a reason for a higher 30-day mortality. To improve outcome, specific precautions are suggested when operating on under- as well as overweight CRC patients. We also suggest that the registry introduces a better marker than BMI for central visceral fat-the link between obesity and cancer development. Further studies are needed to analyze the findings in detail and to study long-term effects.