The role of body composition and pulmonary function in predicting long-term survival after lung cancer surgery

The TNM Classification of Malignant Tumors is the primary tool for staging lung cancer, guiding treatment and prognosis. Host factors like body composition and pulmonary function are barely considered for treatment decisions and prognosis. Therefore, the objective of this study was to assess the association between body composition and pulmonary function with overall survival in patients undergoing surgery for lung cancer.

Patients undergoing surgery for suspected lung cancer between 2012 and 2018 were included. Computed tomography (CT) scans were analyzed at the third lumbar (L3) vertebra. Skeletal muscle tissue (SM), visceral adipose tissue (VAT), and subcutaneous adipose tissue (SAT) index and radiation attenuation (RA) were assessed. Lower RA indicates increased tissue triglycerides. Pulmonary function was defined as percentage of predicted forced expiratory volume in 1 s (FEV1%). Patients with a FEV1% lower than 80 % were considered to have a decreased pulmonary function according to literature. SM, VAT and SAT were corrected for sex and age by calculating Z-scores. Age groups were defined as < 60 years, ≥60 and ≤70 years, or >70 years. Means with standard deviation (SD) or medians with interquartile range (IQR) were reported. Multivariate cox-regression analysis with hazard ratios (HR) and 95 % confidence intervals (CI), and Kaplan-Meier analysis were used. Covariates were added to the model by backwards stepwise selection. Multivariate linear regression was used to study the association between body composition and pulmonary function.

We included 530 patients, with a mean age of 67 (SD 9.5) years, 57.5 % was male. Overall median survival was 64 months (IQR 30-96). Survival analysis was conducted on 441 patients with malignant disease and all covariates available. Z-SAT-RA (HR 1.182, 95 % CI 1.050-1.390, p = 0.006), FEV1% (HR 0.987 95 % CI 0.980-0.993, p < 0,001) and Z-SM-index (HR 0.865 95 % CI 0.757-0.988, p = 0.032) were associated with survival. The impact of high SAT-RA was particularly apparent in patients with high FEV1%. Kaplan-Meier analysis showed that patients with high, compared to low, FEV1% had significantly better overall survival in both localized and regional stage disease. Z-VAT-RA and Z-VAT-index were not associated with survival. ASA-III classification (B = -2.914, p = 0.005) and Z-SMRA (B = 3.007, p < 0.001) were associated with FEV1% in multivariate linear regression analysis.

Low FEV1%, low SM-index, and high SAT-RA were associated with decreased survival in patients that underwent surgery for lung cancer. Host phenotypes based on body composition and pulmonary function could play an important role in treatment decision making.