The effect of body mass index at diagnosis on survival of patients with squamous cell head and neck carcinoma.

The aim of this study is to investigate the prognostic role of body mass index (BMI) on survival from head and neck cancer (HNC). We performed a pooled analysis of studies included in the International Head and Neck Cancer Epidemiology consortium. We used Cox proportional hazards models to estimate the adjusted hazard ratios (HR) for overall survival and HNC-specific survival, and we stratified the results according to cancer site. The study included 10,177 patients from 10 studies worldwide. Underweight patients had lower overall survival (HR=1.69, 95% CI: 1.31-2.19) respect to those having normal weight with consistent results across the HNC sites. Overweight and obese patients had a favourable HNC-specific survival (HR=0.77 (95% CI: 0.70-0.84) and HR=0.80 (95% CI: 0.76-0.84), respectively), with heterogenous results according to HNC site. Our findings show that high BMI values at cancer diagnosis improved the survival rates in patients with HNC, especially among smokers. This association may be explained by residual confounding, reverse causation, and collider stratification bias, but may also suggest that a nutritional reserve may help patients survive HNC cancer.