584P - Fdg-Pet Tumor Load Parameters Measured by Total Lesion Glycolysis as Predictors of Treatment Response and Outcome in Metastatic Colorectal Cancer

Abstract

ABSTRACT Objectives Early metabolic response measured by the change of FDG maximum Standardized Uptake Value (SUVmax) on PET-CT after 1 cycle of chemotherapy in patients with metastatic colorectal cancer (mCRC) can predict negative objective response and is correlated to Overall Survival (OS) (Hendlisz et al. 2011). The aim of this work is to assess the correlation between the change in FDG-PET whole body metabolic tumoral load parameters and the RECIST response, progression free survival (PFS), OS. Methods FDG-PET/CT scans were performed at baseline and on Day 14, in 41 patients with unresectable mCRC undergoing a biweekly chemotherapy regimen. Patients were followed-up for up to 28 months. The change in Functional Tumor Volume (FTV) and Total Lesion Glycolysis (TLG) (TLG = FTV x SUVmean) of all the lesions was calculated using a fixed threshold segmentation algorithm (threshold for segmentation = SUV mean of 30 mm sphere in the right lobe of the liver plus 3 standard deviations) corrected to lean body mass (Wahl et al 2009). Predictive and prognostic value was tested through correlation with RECIST response (using independent dedicated CT), PFS and OS. A cutoff value for TLG responding patients was set at 40% or more decrease in the baseline value. Results 39 patients were evaluable for analysis. The median OS was 20 months (95% CI, 10 to 28), the change in whole body FTV and TLG were significantly related to RECIST response (p-value: 0.015 and 0.0038), to PFS (P-value: 0.009, 0.018) and to OS (p-value: 0.002, 0.0027). Patients with > 40% decrease in TLG have better PFS: median 12 months compared to median 3 months in the rest of the patients [log rank test p-value 0.004; HR 0.31 (95% CI, 0.14 to 0.72)], and a better median OS 27 months compared to 11 months [log rank test p-value 0.05; HR 0.38 (95% CI, 0.14 to 1.04)]. Conclusions Changes in the metabolic tumoral load parameters after one cycle of standard chemotherapy for mCRC are predictors of RECIST response, progression free and overall survival. Disclosure All authors have declared no conflicts of interest.