Association of body mass index and weight change with death in patients with advanced cancer

Conventional diagnostic criteria for cachexia are based on Western studies. The aim of this study was to investigate trends in body mass index (BMI) and the rate of weight change associated with adverse outcomes in Asian patients with advanced cancer.This retrospective cohort study was conducted using the administrative claims database compiled by the Japan Medical Data Center Inc. The study was conducted between April 2014 and September 2022 on patients with advanced cancer. A Cox regression model was used to perform a restricted cubic spline analysis with four knots for BMI and weight change. Additionally, thin-plate smoothed splines were used to generate contour plots of the odds ratios of BMI and weight change for mortality.The study analyzed 48 600 patients. The mean age was 71.9 ± 10 y. There were 33 051 men (68%) and 17 853 deaths (37%). The smoothed splines for BMI showed that low BMI was associated with high hazard ratio (HR, [95% confidence interval]; BMI = 18.5 kg/m2, HR, 1.2; [1.1-1.2]; BMI = 25 kg/m2, HR, 0.9; [0.9-0.9]). The smoothed spline of weight change showed a higher HR with an increasing rate of weight change (weight change rate -10%, HR, 1.1; [1.1-1.2]; weight change rate +10%, HR, 1; [1-1]). In the thin-plate smoothed spline analysis, patients with BMI <17 to 18.5 kg/m2 were at a higher risk for death regardless of weight change.Low BMI, a large degree of weight change, or a combination of both, predicted death in Asian patients with advanced cancer.