High-Dose Transarterial Radioembolization of Hepatic Metastases Using Yttrium-90 Resin Microspheres

<b>Background/Objectives</b>: Over the past few years, high-dose radioembolization (≥150 Gy) has become widely adopted for the treatment of primary liver cancer, while evidence for its application in hepatic metastases is still limited. The aim of this study was to evaluate the safety and efficacy of high-dose transarterial radioembolization (TARE) in patients with hepatic metastases using resin Yttrium-90 (⁹⁰Y) microspheres. <b>Methods</b>: In this retrospective analysis, patients who were treated with high-dose TARE for hepatic metastases with ⁹⁰Y resin microspheres between May 2019 and April 2025 were included. The primary outcomes were treatment efficacy and toxicity assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events v5.0. Treatment efficacy was evaluated based on radiological response according to Response Evaluation Criteria in Solid Tumors version 1.1, time to progression and overall survival (OS). Secondary outcomes included ⁹⁰Y PET/CT post-treatment voxel-based local deposition model dosimetry and its relations to response. <b>Results</b>: A total of 15 patients were included, with hepatic metastases originating from colorectal cancer (<i>n</i> = 11, 73.3%), neuroendocrine tumor (<i>n</i> = 3, 20%) and breast cancer (<i>n</i> = 1, 6.7%). Seven patients (47.7%) had undergone one or multiple prior loco(regional) liver treatments and 13 (86.7%) patients had prior systemic therapy. The median mean tumor absorbed dose was 160.7 Gy (IQR 127.6-245.0 Gy), and the median normal liver parenchyma dose was 40.3 Gy (IQR 21.7-52.3 Gy). Disease control was achieved in all patients, with partial response in 10 patients (66.7%) and stable disease in 5 patients (33.3%) after 3 months. The median OS was 26.5 months (95% CI 24.5 months to no estimate). Two patients (13.3%) experienced grade 3 laboratory toxicity. No grade 4 or 5 toxicities were observed. <b>Conclusions</b>: High-dose TARE with ⁹⁰Y resin microspheres resulted in a high disease control rate and demonstrated a favorable safety profile, even in this heavily pretreated cohort.