Systematic review of prognostic roles of body mass index for patients undergoing lung cancer surgery: does the 'obesity paradox' really exist?

The paradoxical benefit of obesity, the 'obesity paradox', has been recently identified in surgical populations. Our goal was to evaluate by a systematic review with meta-analysis the prognostic role of body mass index (BMI) and to identify whether the 'obesity paradox' exists in lung cancer surgery. Comprehensive literature retrieval was conducted in PubMed to identify the eligible articles. The odds ratios (OR) and hazard ratios (HR) with the corresponding 95% confidence intervals (CI) were used to synthesize in-hospital and long-term survival outcomes, respectively. The heterogeneity level and publication bias between studies were also estimated. Finally, 25 observational studies with 78 143 patients were included in this review. The pooled analyses showed a significantly better long-term survival rate in patients with higher BMI, but no significant benefit of increased BMI was found for in-hospital morbidity. The pooled analyses also showed that overall morbidity (OR: 0.84; 95% CI: 0.73-0.98; P  =   0.025) and in-hospital mortality (OR: 0.78; 95% CI: 0.63-0.98; P  =   0.031) were significantly decreased in obese patients. Obesity could be a strong predictor of the favourable long-term prognosis of lung cancer patients (HR: 0.69; 95% CI: 0.56-0.86; P  =   0.001). The robustness of these pooled estimates was strong. No publication bias was detected. In summary, obesity has favourable effects on in-hospital outcomes and long-term survival of surgical patients with lung cancer. The 'obesity paradox' does have the potential to exist in lung cancer surgery.