Body mass index and survival after surgery for gastric adenocarcinoma: a population-based nationwide cohort study in Finland.

[BACKGROUND] Gastric cancer surgery is associated with significant morbidity. Obesity is a risk factor for short-term complications. However, previous studies on the role of body mass index (BMI) as a predictor of long-term survival have conflicting results, and contemporary population-based data in the Western population are lacking. This study aimed to compare the long-term survival after gastric cancer surgery among patients who were underweight (BMI of <18.5 kg/m), those with normal weight (BMI of 18.5-24.9 kg/m), those who were overweight (BMI of 25.0-29.9 kg/m), and those who were obese (BMI of >30.0 kg/m).

[METHODS] This was a population-based, retrospective, nationwide cohort study in Finland using the Finnish National Esophago-Gastric Cancer Cohort. Patients who underwent gastrectomy with available height and weight data were included. A Cox regression model was used to calculate the 95% CI for 6-month to 5-year survival and 6-month survival, which was adjusted for age, sex (assigned), year of surgery, Charlson Comorbidity Index, pathological p/yp stage, neoadjuvant therapy, type of resection, and Lauren histological type.

[RESULTS] Overall, 1647 patients who underwent gastrectomy for gastric cancer were identified. Of the patients, 64 (3.9%) were underweight, 735 (44.6%) had normal weight, 584 (35.5%) were overweight, and 264 (16.0%) were obese. In the first 6 months, mortality was higher in the overweight group (hazard ratio [HR], 1.663 [95% CI, 1.158-2.389]) than in the normal weight group. However, 6-month to 5-year mortality was the highest in the underweight group (HR, 1.426 [95% CI, 1.019-1.994]) and decreased with increasing BMI (HR, 0.820 [95% CI, 0.708-0.949]). Patients with obesity had the best prognosis (HR, 0.798 [95% CI, 0.655-0.971]).

[CONCLUSION] In this population-based study, higher BMI was associated with better long-term survival after gastric cancer surgery, somewhat offset by higher mortality during the first postoperative months, with patients with obesity having the best overall survival.