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), normal (18.5 to < 23 kg/m), overweight (23 to < 25 kg/m), mildly obese (25 to < 28 kg/m), moderately obese (28 to < 30 kg/m), and severely obese (≥ 30 kg/m). 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.

Conclusion: In patients undergoing curative gastric cancer surgery, those who were overweight or mildly-to-moderately obese (BMI 23 to < 30 kg/m) preoperatively had better OS and DSS than normal-weight patients.