Thoracic muscle mass predicts survival among patients with locally advanced esophageal cancer

Abstract

Background & aims

There is limited literature evaluating muscle mass at the fourth thoracic (T4) vertebrae using computed tomography (CT) images, with no studies evaluating T4 muscle mass in esophageal cancer.

Methods

In this retrospective cohort study, body composition analysis using skeletal muscle index (SMI) was conducted at T4 and L3. Overall survival (OS) and disease-free survival (DFS) were evaluated using Kaplan–Meier curves and log-rank tests, as well as multivariable cox proportional hazards models. Correlation analysis and evaluation of fixed and proportional bias was conducted. Low muscle mass was defined by the lowest quartile of the SMI distribution from the post-neoadjuvant CT: <30.4 cm²/m² (females) and <42.2 cm²/m² (males) for L3, and <35.4 cm²/m² (females) and <52.6 cm²/m² (males) for T4.

Results

Of the 120 patients included, eight (8.2 %) patients had T4-low muscle mass at the staging CT which increased to 25 (25.8 %) at the post-neoadjuvant CT. On multivariable analysis, T4-low muscle mass was associated with worse overall survival (OS) (HR 2.51, 95 % CI 1.47–4.29, p = 0.001) and disease-free survival (DFS) (HR 1.88, 95 % CI 1.09–3.24, p = 0.022). T4-SMI was higher than L3-SMI at both the staging (65.4 ± 13.6 cm²/m² versus 51.1 ± 10.0 cm²/m², p < 0.001) and post-neoadjuvant (57.8 ± 12.7 cm²/m² versus 45.8 ± 9.3 cm²/m², p < 0.001) CT scans. The correlation (R-value) between T4 and L3 SMI was greater than 0.6 (0.62–0.81) for all staging intervals.

Conclusion

Our findings support using low muscle mass at T4 as a prognostic indicator for OS and DFS. These findings can be extrapolated to tumor groups, such as lung cancer, where L3-low muscle mass status is not routinely available.