Prognostic significance of preoperative CT-based sarcopenia in locally advanced rectal cancer: a multicenter retrospective study.

Objectives: The association between preoperative CT-based sarcopenia and prognosis in locally advanced rectal cancer (LARC) remains unclear. The aim of this study was to investigate the relationship between CT-based sarcopenia and clinical outcomes in patients with LARC.

Materials And Methods: This multicenter retrospective study analyzed 503 LARC patients who underwent radical resection in three tertiary hospitals in China from January 2018 to June 2021 and were pathologically confirmed. All patients were followed for a period of at least three years. Clinical, pathological, and imaging data were carefully collected. According to the sex-specific skeletal muscle index (SMI), patients were evaluated for the presence of CT-based sarcopenia. The SMI was obtained by measuring the cross-sectional muscle area and standardizing it by the height of different patients. The primary endpoint was post-operative overall survival (OS), and the secondary endpoint included disease-free survival (DFS), postoperative complications, prolonged length of stay (LOS), readmission, and cancer-specific survival (CSS).

Results: This study included 503 patients [mean age: 61.5 ± 10.8 years; 353 male (70.2%)], who were divided into the non-sarcopenic group (375 patients, 74.5%) and the sarcopenic group (128 patients, 25.5%). Over a mean follow-up period of 47 months (range 4-73), a total of 108 (21.4%) deaths and 162 (32.2%) combined endpoints, including recurrence or metastasis, were observed. Multivariate Cox regression analysis revealed that CT-based sarcopenia (hazard ratio [HR], 2.41; 95% confidence interval [CI], 1.49 ~ 3.87; P < 0.001) was independently associated with worse OS in LARC patients over a three-year period, but was not associated with shorter DFS (HR, 1.34; 95% CI, 0.89 ~ 2.03; P = 0.163). CT-based sarcopenia was not significantly associated with postoperative complications of grade II or greater (odds ratio [OR]: 1.29, 95% CI: 0.62 ~ 2.68, P = 0.496) or prolonged LOS (OR: 1.05, 95% CI: 0.6 ~ 1.86, P = 0.853). However, sarcopenic patients showed a higher risk of readmission (OR: 5.53, 95% CI: 1.57 ~ 19.5, P = 0.008) and a significant correlation with poorer CSS (HR: 2.78, 95% CI: 1.64 ~ 4.72, P < 0.001). Kaplan-Meier analysis showed that sarcopenic LARC patients had a significantly higher cumulative hazard of OS compared to non-sarcopenic patients (P < 0.001, log-rank test). Similar patterns of association were observed in subgroup analyses (all P values for interaction > 0.05).

Conclusions: Preoperative CT-based sarcopenia is independently associated with decreased OS, CSS, and an elevated risk of readmission in patients with LARC. These findings emphasize the importance of identifying sarcopenic patients at higher risk for adverse outcomes and suggest that interventions aimed at improving physical strength and endurance may play a critical role in informing treatment strategies and guiding clinical decisions.