Impact of CT-Based Body Composition Analysis on Postoperative Survival in Patients Undergoing Colorectal Cancer Surgery

Background Colorectal cancer (CRC) remains a leading cause of cancer-related mortality worldwide, underscoring the need for reliable prognostic biomarkers. Emerging evidence suggests that body composition parameters may influence cancer outcomes. This study aimed to evaluate whether low skeletal muscle mass, high visceral fat, and their coexistence predict long-term outcomes in patients with CRC. Methods This retrospective study included 103 patients with pathological stage III CRC who underwent curative resection. Skeletal mass index (SMI) and visceral fat index (VFI) were calculated from preoperative CT images at the L3 level by dividing skeletal muscle and visceral fat areas by height squared. Overall survival (OS) and recurrence-free survival (RFS) were analyzed using Kaplan-Meier and Cox regression models. Results Low-SMI and high-VFI were present in 52.4% and 28.2% of patients, respectively. In Cox regression, low-SMI independently predicted poor OS (HR 5.14, P = 0.004), while high-VFI was an independent predictor of RFS (HR 2.72, P = 0.012). In the four-group analysis, for OS, both the coexistence of low-SMI and high-VFI (low-SMI-high-VFI, P = 0.021) and low-SMI-only ( P = 0.023) had worse survival than controls, with no difference between them ( P = 0.77). For RFS, high-VFI alone was associated with worse prognosis compared with controls ( P = 0.040). Low-SMI-high-VFI patients had significantly poorer prognosis than both controls ( P < 0.001) and low-SMI alone ( P = 0.024). Conclusions Low skeletal muscle mass and high visceral fat are associated with poorer OS and RFS, respectively. The coexistence of them may have an additive adverse association with recurrence risk in patients with low skeletal muscle mass. Preoperative body composition assessment may facilitate risk stratification in CRC, and improving these parameters could potentially contribute to better oncologic outcomes.