The relationship between computed tomography derived skeletal muscle index, psoas muscle index and clinical outcomes in patients with operable colorectal cancer.

Abstract

Computed tomography-based measures of body composition are emerging as important prognostic factors for patients with colorectal cancer (CRC). The aim of this study was to examine the relationship between total skeletal muscle index (SMI), psoas muscle index (PMI) and clinical outcomes in patients with operable CRC. A retrospective cohort study of prospectively maintained database at Glasgow Royal Infirmary. CT image at L3 was carried out to assess total skeletal and psoas muscle areas and these were normalized for height squared to calculate SMI and PMI respectively. Patients were classified into high and low groups using calculated optimal thresholds and their relationship to clinical outcomes was studied using logistic regression analysis. Of the 1002 patients included, 55% were male, 50% had low SMI and 42% had low PMI. A moderate correlation was found between total skeletal muscle and psoas areas (rs=0.70, p<0.001). On univariate analysis, low SMI was associated with length of hospital stay (OR, 1.47; 95% CI, 1.15-1.89, p=0.002) and overall survival (HR, 2.29; 95% CI, 1.47-3.58, p<0.001). On multivariate analysis, low SMI was independently associated with length of hospital stay (HR 1.32; 95% CI, 1.02-1.70, p<0.05). On univariate analysis, low PMI was associated with length of hospital stay (OR, 1.34; 95% CI, 1.04-1.73, p<0.05) and overall survival (OR, 1.43; 95% CI, 1.10-1.86 p<0.01). On multivariate analysis, low PMI was not independently significant. The present study shows that though both total skeletal muscle index and psoas muscle index were directly associated and had prognostic value, total skeletal muscle index had independent prognostic value in patients with operable CRC.