Objective: To assess the correlation of primary colorectal cancer (CRC) lesions' maximum standardized uptake value (SUVmax) and tumor to normal tissue SUVmax ratio (T/N ratio) detected by ¹⁸F-deoxyglucose positron emission computed tomography (¹⁸F-FDG PET-CT) imaging with the postoperative prognosis.
Methods: Clinicopathological data of 92 CRC patients who underwent curative resection after the PET-CT examination and received ¹⁸F-FDG PET-CT examination from January 2009 to December 2013 in the First Affiliated Hospital of Sun Yat-sen University were reviewed retrospectively. The correlation of SUVmax and T/N ratio in primary lesions with clinicopathological factors was analyzed. The optimal cutoff point of disease-free survival time of SUVmax, T/N ratio and the maximum tumor diameter were investigated by using ROC curve analysis. Association of clinicopathological factors and prognosis was examined and the Cox proportional hazard regression model was used in the multivariate analysis.
Results: Primary SUVmax was associated with tumor TNM staging, location, differentiation degree and the maximum tumor diameter, while T/N ratio was only associated with pathological type (all P<0.05). The optimal cutoff point of disease-free survival time of SUVmax, T/N ratio and the maximum tumor diameter were 12.2 (sensitivity 67.6%, specificity 63.6% ), 6.9 (sensitivity 51.4%, specificity 74.5%) and 4.3 cm (sensitivity 56.8%, specificity 80.0%) respectively. Univariate analysis showed that age, TNM staging, tumor location, differentiation degree, the maximum tumor diameter, T/N ratio and CA125 level were significant predictors of survival. Multivariate analysis demonstrated that TNM staging (P=0.000, OR=3.98, 95% CI:2.12-7.45), tumor location (P=0.009, OR=0.43, 95% CI:0.23-0.81), tumor differentiation degree (P=0.001, OR=7.52, 95% CI:2.12-25.9) and T/N ratio (P=0.008, OR=2.92, 95% CI:1.33-6.411) were independent predictors of survival. However, SUVmax was not independent predictor of disease-free survival.
Conclusion: For postoperative prognosis of colorectal cancer patients, T/N ratio is more valuable than the of primary tumor SUVmax.