Abstract No. 154 Using Post–Yttrium-90 PET/CT To Identify Tumors More Likely to have Complete Pathologic Necrosis After Radiation Segmentectomy for Hepatocellular Carcinoma

To evaluate complete pathologic necrosis (CPN) following 90Y radiation segmentectomy using resin microspheres for hepatocellular carcinoma (HCC), and the post 90Y PET/CT characteristics associated with CPN. All HCC patients receiving 90Y radioembolization from 2014 to June 2023 (n=176) were assessed in this retrospective, institutional review board–approved study. Patients undergoing radiation segmentectomy (1-2 segments treated using single compartment MIRD model) followed by resection or transplant were included (n=13). 90Y procedure characteristics and histology results were collected. Microsphere distribution per cc were calculated based on a previously described formula. Minimum absorbed dose to 50% of the tumor (D50) and volume of tumor receiving 2 cc (p = 0.04). Additionally, CPN was achieved in 4/6 (66%) patients with a D50 > 215 Gy and 6/8 (75%) patients with tumoral microsphere distribution per cc of >45,000. HCC treated with 90Y resin-based radiation segmentectomy results in a high CPN rate. Undertreated tumor volume (V0-100Gy of >2 cc) can be identified on post-treatment PET/CT and predicts CPN.