Preoperative Body Mass Index, Waist Circumference, and Mortality After Major Cancer Surgery: A Nationwide Cohort Study in Korea

Background: Body mass index (BMI) and waist circumference (WC) were used to evaluate nutritional status and obesity. We aimed to examine whether preoperative BMI or WC was associated with mortality after cancer surgery. Methods: This population-based cohort study used data extracted from the National Health Insurance Service database of South Korea. We included adult patients who underwent major cancer surgery with curative intent between January 1, 2016, and December 31, 2020. Results: A total of 87,220 patients were included in the final analysis, and 1,374 (1.6%) died within 90 days after cancer surgery. In the multiple logistic regression model, the BMI 18.5/kg/m2 and 35 kg/m2 groups showed 1.98-fold (odds ratio [OR], 1.98; 95% confidence interval [CI], 1.58-2.49; P < 0.001) and 2.60-fold (OR, 2.60; 95% CI, 1.25-5.40; P < 0.001) higher 90-day mortality after cancer surgery than did the BMI 18.5-24.9 kg/m2 group. The 25.0-29.9 kg/m2 (P = 0.144) and 30.0-34.9 kg/m2 (P = 0.105) BMI groups did not show significant differences compared to the BMI 18.5-24.9 kg/m2 group. Compared with the normal WC group, the high (P = 0.052) and very high (P = 0.232) WC groups also did not show significant differences in terms of 90-day mortality. Conclusions: Preoperative BMI 18.5 kg/m2 and 35 kg/m2 is associated with an elevated risk of 90-day mortality after major cancer surgery. However, preoperative WC was not significantly associated with 90-day mortality after cancer surgery.