Premorbid body mass index and mortality in patients with lung cancer: A systematic review and meta-analysis

Objectives We aimed to assess the association between premorbid obesity, measured using body mass index (BMI) and lung cancer-related mortality, through a systematic review and meta-analysis. Materials and Methods Observational studies reporting statistical measures of association between premorbid BMI categories and lung cancer-related mortality were included in our study. We estimated hazard ratios (aHR) with 95% confidence intervals (CI), comparing lung cancer-related mortality across BMI categories. The main outcome measure was lung cancer-related mortality in obese (BMI≥30kg/m 2 ) and overweight participants (BMI 25.0–29.9kg/m 2 ), compared with normal BMI participants. Results We included 14 studies (including 2 pooled cohort studies) comprising 3,008,137 cancer-free participants at inception, reporting 28,592 lung cancer-related deaths. On meta-analysis, we observed a significantly lower lung cancer-related mortality in overweight (aHR, 0.76; 95% CI, 0.68–0.85) and obese (aHR, 0.68, 95% CI; 0.57–0.81) participants as compared to participants with normal BMI, with considerable heterogeneity; after excluding one study with large effect size, a more conservative and consistent association was observed between BMI and lung cancer-related mortality (overweight vs. normal BMI: aHR, 0.84; 95% CI, 0.79–0.90; obese vs. normal BMI: aHR, 0.81; 95% CI, 0.75–0.87), with moderate heterogeneity. Were similar in men vs. women, non-smokers vs. smokers, and Western vs Asia-Pacific populations. Conclusions Based on meta-analysis, we observed an independent protective association between premorbid obesity and lung cancer-related mortality. This association was observed across sex, smoking status and geographic region. Further studies are needed to prospectively study this association.