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

Abstract

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.