Muscle quality, not quantity, is associated with outcome after colorectal cancer surgery

Introduction: Emerging evidence suggests that deconditioned patients benefit most from prehabilitation before colorectal cancer surgery. So far, selecting patients with poor muscle status and high perioperative risk remains challenging. Therefore, this study evaluates the potential of the CT-derived Skeletal Muscle Index (SMI), representing muscle mass, and of the Muscle Radiation Attenuation (MRA), a measure of muscle quality, for risk stratification in colorectal cancer patients.Methods: In this retrospective, single-center observational study, 207 patients with resection of colorectal adenocarcinoma between January 2016 and December 2020 were included. The Charlson comorbidity index (CCI), postoperative complications, length of hospital stay, and survival were recorded. Data were analyzed using multivariable linear, logistic, and Cox proportional hazards regression models adjusted for age, sex, BMI, CCI, neoadjuvant therapy, tumor stage, and surgery type.Results: An increase of the MRA was associated with fewer postoperative complications (anastomotic leakage and pneumonia) and lesser severity according to the Clavien-Dindo classification, shorter hospital stays, and prolonged survival (Hazard ratio: 0.63 [95%CI: 0.49-0.81], p < 0.001). No relevant associations were found between the SMI and postoperative complications, length of hospital stay, or survival.Conclusion: The easy-to-raise MRA serves as a more reliable tool than the SMI for identifying high-risk patients with poor muscle status before colorectal surgery. Those patients may benefit most from prehabilitation, which has to be proven in future interventional trials.