18F-FDG and 11C-acetate PET/CT predicts treatment response and survival of a cohort of BCLC B-C patients treated by Y90-SIRT

573 Objectives The predictive role of pretreatment 18F-FDG (FDG) PET/CT in Yttrium-90 (Y90) SIRT for inoperable HCC patients with FDG-avid tumor is well documented. However, it is not well studied in HCC cases that are non-avid for FDG because these lesions may also include non-HCC cirrhotic nodules lumped together as a single “FDG-non-avid” category by others. We prospectively evaluate the value of 11C-acetate (ACT) & FDG PET/CT for prediction of treatment efficacy and post-treatment survival in a cohort of BCLC B-C patients. Methods During year 2012-14, 18 HCC patients staged as BCLC B-C were prospectively referred for pretreatment ACT & FDG PET/CT (M:16, F:2; mean age=56.8±17.7y; 17 HBV, 1 HCV) within 2 wk before Y90-SIRT (dose range:1.30~3.57GBq, mean=2.30±0.69GBq). Post-treatment PET/CT was performed at 2 mo after Y90-SIRT. Metabolic tumor burden (MTB) was defined as the “summation of the product of individual lesion SUVmean×lesion volume” of all HCC lesions on either ACT or FDG PET. Metabolic response was assessed as the “% change in MTB” between post and pretreatment PET/CT, and “a reduction of >50%” was classified as good responder. The predictive value of good/poor responder for 2-y overall survival (OS) was analyzed. Results On pretreatment PET/CT, 8/18 patients were primarily avid by ACT and 10/18 by FDG. On post Y90-SIRT PET/CT, ACT-avid patients showed significantly better treatment response than FDG-avid patients (good responders=100% [8/8] vs 50% [5/10], P 24mo, P Conclusions BCLC B-C patients with preferred avidity for ACT (FDG-non-avid HCC) on pretreatment PET/CT might have a higher chance to be good responder to Y90-SIRT. Metabolic good responder evaluated by the complementary use of post-treatment ACT & FDG PET/CT might have a better 2-y OS.