Preoperative thoracic muscle area on computed tomography predicts long-term survival following pneumonectomy for lung cancer

Abstract

Objectives: To assess the prognostic role of thoracic muscle as quantified on preoperative computed tomography (CT) for the estimation of overall survival (OS) following pneumonectomy.

Methods: Muscle cross-sectional area (CSA) at the level of the fifth (T5) and eighth (T8) thoracic vertebra was measured on CT scans of consecutive patients with lung cancer prior to pneumonectomy. We stratified patients into high and low muscle groups using the gender-specific median of muscle CSA as separator and estimated associations of muscle CSA and OS using the Kaplan-Meier analysis. Multivariable logistic regression adjusted for body mass index, Charlson comorbidity index (includes age), forced expiratory volume in the first second as a % of predicted, sex, race, smoking status, tumour stage and prior lung cancer treatment was performed.

Results: A total of 128 patients were included (61.0 ± 10.6 years of age, mean body mass index of 26.9 kg/m2, 55.5% men). The T8 level showed fewer artefacts and strong correlation with the T5 level (Pearson's rho = 0.904). T8 CSA was therefore used for subsequent analyses. Mean T8 CSA was 118.5 cm2 (median 115.3 cm2) in men and 75.2 cm2 (median 74.0 cm2) in women. During a median follow-up of 23.6 months (interquartile range 39.3), 65 patients (50.8%) died, of whom 41 were in the low muscle group. The Kaplan-Meier analysis showed significantly longer OS in the high muscle group (log-rank P = 0.02). Multivariable analysis showed an independent association of muscle CSA and OS (P = 0.02) with a hazard ratio of 0.80 (confidence interval 0.67-0.98) per 10-cm2 increment.

Conclusions: Thoracic muscle is independently associated with long-term overall survival following pneumonectomy for lung cancer and may contribute to refined survival estimates in this population.

Irb protocol: Protocol #2017P000650, approved 21 April 2017.

Keywords: Computed tomography; Lung cancer; Muscle; Overall survival; Pneumonectomy; Risk stratification.