Using Voxel-based Dosimetry to evaluate sphere concentration and tumor dose in Hepatocellular Carcinoma treated with Y-90 Radiation Segmentectomy with glass microspheres.

PURPOSE: To utilize voxel-based dosimetry following radiation segmentectomy to understand microsphere distribution and validate current literature regarding radiologic and pathologic outcomes.

METHODS: A retrospective, single-center analysis of solitary HCC patients (n=56) treated with Y90 radiation segmentectomy with glass microspheres (TheraSphere; Boston Scientific, Marlborough, MA, USA) from 2020 to 2022 was performed. Post-treatment voxel-based dosimetry was evaluated using Mirada DBx Build 1.2.0 Simplicit90 Y software and utilized to calculate sphere concentration to tumor, as well as D70 (minimum dose to 70% total tumor volume), D90 , and D99 . Time to progression (TTP), treatment response, and adverse events were studied.

RESULTS: Fifty-six solitary tumors were analyzed with a median tumor diameter of 3.4cm (range 1.2-6.8cm) and median tumor absorbed dose of 732Gy (range, 252-1776Gy). Median sphere activity (SA) at time of delivery was 1446Bq (range, 417-2621Bq). Median tumor sphere concentration was 12,868 spheres/mL (range, 2,655-37,183 spheres/mL). Sphere concentration into tumor and normal tissue inversely correlated with perfused treatment volume (R2 =0.21 and 0.39, respectively). Of the 51 tumors with post-treatment imaging, objective response was noted in 49 patients (96%) and complete response in 42 patients (82%). The median TTP was not reached with a 2-year progression rate of 11%. 15 patients underwent liver transplant. Median tumor necrosis was 99% (range, 80-100%). Lower tumor volumes and higher D99 were associated with CPN (p<0.001 and p=0.022, respectively).

CONCLUSION: Voxel-based dosimetry following Y90 radioembolization can be utilized to account for sphere deposition and distribution into tumor. Ablative RS with high SA yields durable radiologic and pathologic outcomes.