Association of preoperative CT-derived visceral adipose tissue index with synchronous metastasis and metastasis-free survival after curative-intent surgery in colorectal cancer

Background: To evaluate whether computed tomography (CT)-derived visceral adipose tissue index (VATI) is associated with synchronous metastasis and metastasis-free survival (MFS) after curative-intent surgery in colorectal cancer (CRC). Methods: This retrospective two-center study included patients with newly diagnosed CRC who underwent abdominal CT within 1 month before diagnosis or initial treatment between January 2019 and December 2022 (n = 468; metastatic CRC [mCRC], n = 77; non-metastatic CRC [nmCRC], n = 391). For the synchronous metastasis analysis, mCRC and nmCRC were propensity score matched 1:1 for age, sex, carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9), study center, and tumor location (77 pairs), and multivariable logistic regression was performed. For the MFS analysis, the surgical nmCRC cohort was stratified by sex-specific median VATI into low-VATI (n = 195) and high-VATI (n = 196) groups, and Kaplan-Meier and Cox proportional hazards analyses were performed. Among patients who developed postoperative metastasis (n = 96), an exploratory descriptive comparison was performed between early (≤ 2 years, n = 76) and late (> 2 years, n = 20) metastasis groups. Results: After matching, mCRC showed higher subcutaneous adipose tissue index (SATI), VATI, and visceral-to-subcutaneous fat area ratio (VSR) than nmCRC. VATI was independently associated with synchronous metastasis (OR, 1.110; 95% CI, 1.067-1.155; p < 0.001), whereas SATI and VSR were not. In the surgical nmCRC cohort, the high-VATI group had shorter MFS (log-rank p = 0.001). On multivariable Cox analysis, VATI remained independently associated with shorter MFS (HR, 1.017; 95% CI, 1.003-1.032; p = 0.021), together with CA19-9, CEA, N stage, and lymphovascular invasion (LVI). In the exploratory descriptive comparison, no statistically significant differences in body composition metrics were observed between the early and late metastasis groups. Conclusion: Preoperative CT-derived VATI is a reproducible opportunistic imaging biomarker associated with synchronous metastasis and shorter MFS after curative-intent surgery and may help refine risk stratification and postoperative surveillance in CRC, although prospective validation is required before routine clinical application.