Usefulness of metabolic activity of adipose tissue in FDG PET/CT of colorectal cancer

Purpose To determine the relationship between metabolic activity of adipose tissue on FDG PET/CT and prognosis in colorectal cancer. Methods A total of 176 colorectal cancer patients with curative surgical resection were retrospectively enrolled. Volume and metabolic activity of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) on FDG PET/CT images were measured. The maximum standardized uptake value (SUV) of primary tumor (SUVtumor) was also obtained. Univariate analysis with log-rank test and multivariate Cox regression analyses were used to evaluate prognostic values of volume and metabolic activity of SAT and VAT as well as SUVtumor and clinicopathologic factors. Results Of 176 patients, 26 experienced recurrence during follow-up. SUVtumor showed significant correlation with serum C-reactive protein level ( r = 0.242, p = 0.001), SUV of VAT ( r = 0.167, p = 0.026), and size of primary tumor ( r = 0.341, p < 0.001). In univariate analysis with log-rank test, SUV of VAT ( p = 0.009) and SAT ( p = 0.006), volume of VAT ( p = 0.015), N stage ( p < 0.001), M stage ( p < 0.001), tumor involvement of resection margin ( p = 0.001), and lymphatic invasion ( p = 0.024) were significantly associated with recurrence-free survival (RFS). However, SUVtumor showed no significant association with RFS. In multivariate Cox regression analysis, SUV of VAT ( p = 0.016), presence of lymph node metastasis ( p < 0.001), and tumor involvement of resection margin ( p = 0.011) were independent prognostic factors for RFS. Conclusions The SUV of VAT in patients with colorectal cancer is significantly associated with FDG uptake of primary tumor. It is an independent predictor for RFS.