Body mass index and mortality in patients with gastric cancer: a large cohort study

Background The effects of obesity on prognosis in gastric cancer are controversial. Aims To evaluate the association between body mass index (BMI) and mortality in patients with gastric cancer. Methods A single-institution cohort of 7765 patients with gastric cancer undergoing curative gastrectomy between October 2000 and June 2016 was categorized into six groups based on BMI: underweight (<18.5 kg/m(2)), normal (18.5 to < 23 kg/m(2)), overweight (23 to < 25 kg/m(2)), mildly obese (25 to <28 kg/m(2)), moderately obese (28 to < 30 kg/m(2)), and severely obese (>= 30 kg/m(2)). Hazard ratios (HRs) for overall survival (OS) and disease-specific survival (DSS) were calculated using Cox proportional hazard models. Results We identified 1279 (16.5%) all-cause and 763 (9.8%) disease-specific deaths among 7765 patients over 83.05 months (range 1.02-186.97) median follow-up. In multivariable analyses adjusted for statistically significant clinicopathological characteristics, preoperative BMI was associated with OS in a non-linear pattern. Compared with normal-weight patients, underweight patients had worse OS [HR 1.42; 95% confidence interval (CI) 1.15-1.77], whereas overweight (HR 0.84; 95% CI 0.73-0.97), mildly obese (HR 0.77; 95% CI 0.66-0.90), and moderately obese (HR 0.77; 95% CI 0.59-1.01) patients had better OS. DSS exhibited a similar pattern, with lowest mortality in moderately obese patients (HR 0.58; 95% CI 0.39-0.85). Spline analysis showed the lowest all-cause mortality risk at a BMI of 26.67 kg/m(2). Conclusion In patients undergoing curative gastric cancer surgery, those who were overweight or mildly-to-moderately obese (BMI 23 to < 30 kg/m(2)) preoperatively had better OS and DSS than normal-weight patients.