Prognostic Impact of Total Lesion Glycolysis (TLG) from Preoperative (18)F-FDG PET/CT in Stage II/III Colorectal Adenocarcinoma: Extending the Value of PET/CT for Resectable Disease

SIMPLE SUMMARY: PET/CT is rarely performed initially in resectable colorectal cancer and is usually considered for detection of distant metastasis. However, we perceived another potential role of PET/CT in addition to diagnosis and staging, which is providing prognostication of the oncologic outcome by PET parameters extracted from initial PET/CT before surgery. This study evaluated the prognostic role of preoperative 18F-FDG PET/CT in 327 stage II/III colorectal cancer patients and comprehensively investigated the PET parameters with multiple threshold levels to select optimal parameters most robustly related to DFS. Several PET parameters including SUVmax, MTV2.5, MTV3, TLG2.5, TLG3, and TLG30% were significantly related to DFS, with TLG2.5 retaining statistical significance in multivariate analysis with other clinicopathologic prognostic factors. Prognostication with PET/CT at the time of initial diagnosis has substantial benefits over pathologic prognostic factors available only after surgery by giving oncologists an opportunity to consider treatment intensification or de-intensification before initiation of treatment. ABSTRACT: We investigated the prognostic role of metabolic parameters from preoperative (18)F-FDG PET/CT in stage II/III colorectal adenocarcinoma. A total of 327 stage II/III colorectal adenocarcinoma patients who underwent curative resection were included. The maximal standard uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were analyzed for optimal cut-offs and their effect on DFS. Differences in DFS rates and hazard ratios for DFS between cut-offs were statistically significant in SUVmax, MTV2.5, MTV3, TLG 2.5, TLG3, and TLG30%. Factors significantly related to DFS in univariate Cox regression were age, sex, stage, preoperative CEA, SUVmax, MTV2.5, MTV3, TLG2.5, TLG3, and TLG30%. Age, sex, preoperative CEA, and TLG2.5 (p = 0.009) sustained statistically significant difference in multivariate analysis. The 1-, 3-, and 5-year DFS rates for TLG2.5 ≤ 448.5 were 98.1%, 79.6%, and 74.8%, significantly higher than 78.4%, 68.5%, and 61.1% of TLG2.5 > 448.5, respectively (p = 0.012). TLG, a parameter indicating both the metabolic activity and metabolic volume, was the strongest predictor independently associated with DFS, among several PET parameters with statistical significance. These results suggest the potential prognostic value of preoperative (18)F-FDG PET/CT in stage II/III resectable colorectal cancer.