Post-diagnosis BMI change is associated with non-small cell lung cancer survival

Background Body mass index (BMI) change after a lung cancer diagnosis has been associated with non-small cell lung cancer (NSCLC) survival. This study aimed to quantify the association based on a large-scale observational study. Methods Included in the study were 7,547 NSCLC patients with prospectively collected BMI data from Massachusetts General Hospital and Brigham and Women's Hospital/Dana Faber Cancer Institute. Cox proportional hazards regression with time-dependent covariates was used to estimate effect of time varying post-diagnosis BMI change rate (% per month) on overall survival (OS), stratified by clinical subgroups. Spline analysis was conducted to quantify the non-linear association. A Mendelian Randomization (MR) analysis with a total of 3,495 patients further validated the association. Results There was a J-shape association between post-diagnosis BMI change and OS among NSCLC patients. Specifically, a moderate BMI decrease (0.5-2.0; HR = 2.45, 95% CI = 2.25-2.67) and large BMI decrease ({>= 2.0; HR = 4.65, 95% CI = 4.15-5.20) were strongly associated with worse OS, whereas moderate weight gain (0.5-2.0) reduced the risk for mortality (HR = 0.78, 95% CI = 0.68-0.89) and large weight gain (>= 2.0) slightly increased the risk of mortality without reaching statistical significance (HR = 1.10, 95% CI = 0.86-1.42). MR analyses supported the potential causal roles of post-diagnosis BMI change in survival. Conclusions This study indicates that BMI change after diagnosis was associated with mortality risk. Impact Our findings, which reinforce the importance of post-diagnosis BMI surveillance, suggesting that weight loss or large weight gain maybe unwarranted.