Correlation of Y90-absorbed radiation dose to pathological necrosis in hepatocellular carcinoma: confirmatory multicenter analysis in 45 explants.

PURPOSE: To study the correlation between absorbed perfused liver dose using Y90 radioembolization and degree of hepatocellular carcinoma (HCC) necrosis in liver explants in a multicenter cohort analysis METHODS: A retrospective analysis of 45 HCC patients treated between 2014 and 2017 is presented. Inclusion criteria were treatment-naïve solitary HCC ≤ 8 cm and Child-Pugh A liver status using the radiation segmentectomy approach. All patients underwent liver resection or transplantation (LT). Liver explants were examined per institutional routine protocols to assess histopathological viability of HCC. Tumor pathological necrosis was classified into complete (100% necrosis), extensive (> 50% and ≤ 99%) necrosis, and partial (< 50%) necrosis. Absorbed perfused liver doses were estimated using MIRD calculations. Associations between dose and degree of necrosis were studied. RESULTS: Thirty-four (76%) patients underwent LT, and 11 (24%) patients underwent hepatic resection. Median radiation dose was 240 (IQR: 136-387) Gy. Thirty (67%) patients had complete pathologic necrosis (CPN) at explant, while 10 (22%) and 5 (11%) had extensive and partial necrosis, respectively. There were significant differences among perfused liver doses that exhibited partial, extensive, and complete necrosis (p = 0.001). Twenty-four out of twenty-eight (86%) patients who had dose > 190 Gy achieved CPN, while 11/17 (65%) who had < 190 Gy did not (Fisher's exact test; p = 0.001). Using binary logistic regression, only absorbed radiation dose was significantly associated with CPN (p = 0.01), while tumor size was not (p = 0.35). All patients receiving > 400 Gy exhibited CPN. CONCLUSION: Radiation segmentectomy for early HCC with ablative dosing > 400 Gy results in CPN. This represents the new standard target dose for radiation segmentectomy.