Associations of CT-Derived Skeletal Muscle Index and Density With Postoperative Outcomes Following Colorectal Cancer...

Preoperative skeletal muscle index (SMI) and skeletal muscle density (SMD) are gaining attention as predictors of postoperative outcomes following colorectal cancer (CRC) surgery. We examined the associations between computed tomography (CT)-based SMI and SMD with postoperative outcomes following CRC resection.

This was a retrospective cohort study of patients who were surgically treated for CRC at a regional hospital in Baton Rouge, Louisiana, United States, from October 2018 to February 2024. CT-based SMI (cm²/m²) and SMD (Hounsfield units) at the third lumbar vertebra (L3) were used as continuous and binary predictors in multivariable analyses. Low SMI and low SMD were each defined based on two common definitions. Outcomes included length of stay (LOS), severe postoperative complications, discharge location, 90-day mortality and overall mortality (OM). The associations of SMI and SMD with LOS were examined using negative binomial regression. Logistic regression was used to examine the associations of SMI and SMD with severe postoperative complications and discharge location. Survival analysis was used to determine the associations of SMI and SMD with 90-day mortality and OM.

A total of 415 patients (mean age 63.7, SD 13.2) were included in the analysis, of whom 189 (45.5%) were females. The median LOS was 4 days, while 50 (12.0%) of patients experienced at least one severe postoperative complication. A total of 30 (7.2%) patients were discharged to a non-home location, while 12 (2.9%) patients died within 90 days. Over a median follow-up of 31.6 months, 75 (18.1%) patients died. In multivariable analyses, each 5-unit decrease in SMD was associated with increased LOS (incidence rate ratio [IRR] 1.06, 95%CI 1.02-1.10, p = 0.003), greater odds of severe postoperative complications (odds ratio [OR] 1.25, 95%CI 1.02-1.53, p = 0.029) and non-home discharge (OR 1.40, 95%CI 1.09-1.79, p = 0.007), as well as a higher risk of OM (hazard ratio [HR] 1.26, 95%CI 1.09-1.46, p = 0.002). In unadjusted analysis, each 5-unit decrease in SMD was significantly associated with 90-day mortality (HR 1.36, 95%CI 1.04-1.78, p = 0.024). Low SMD based on two different definitions predicted LOS (IRR 1.21, 95%CI 1.05-1.41, p = 0.010; IRR 1.28, 95%CI 1.11-1.48. p < 0.001), while only one definition was significantly associated with a higher risk of OM (HR 1.93, 95%CI 1.08-3.43, p = 0.027). SMI as a continuous or binary predictor was not significantly associated with postoperative outcomes.

CT-based SMD rather than SMI appears to be a more relevant predictor of postoperative outcomes following CRC surgery. Future research should explore whether prehabilitation can improve SMD prior to CRC surgery.