Using Voxel-Based Dosimetry to Evaluate Sphere Concentration and Tumor Dose in Hepatocellular Carcinoma Treated with Yttrium-90 Radiation Segmentectomy with Glass Microspheres

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

Materials And Methods: A retrospective, single-center analysis of patients with solitary hepatocellular carcinoma (N = 56) treated with yttrium-90 (Y) RS with glass microspheres (Therasphere; Boston Scientific, Marlborough, Massachusetts) from 2020 to 2022 was performed. Posttreatment voxel-based dosimetry was evaluated using Mirada DBx Build 1.2.0 SimplicitY software (Boston Scientific) and utilized to calculate sphere concentration to tumor as well as D (minimum dose to 70% total tumor volume), D, and D. Time to progression (TTP), treatment response, and adverse events were studied.

Results: Fifty-six solitary tumors were analyzed with a median tumor diameter of 3.4 cm (range, 1.2-6.8 cm) and median tumor absorbed dose of 732 Gy (range, 252-1,776 Gy). Median sphere activity (SA) at the time of delivery was 1,446 Bq (range, 417-2,621 Bq). Median tumor sphere concentration was 12,868 spheres/mL (range, 2,655-37,183 spheres/mL). Sphere concentration into tumor and normal tissue was inversely correlated with perfused treatment volume (R = 0.21 and R = 0.39, respectively). Of the 51 tumors with posttreatment 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%. Fifteen patients underwent liver transplant. Median tumor necrosis was 99% (range, 80%-100%). Lower tumor volumes and higher D were associated with complete pathologic necrosis (P < .001 and P = .022, respectively).

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