Real World Outcomes of Prescribed Ablative Dose Yttrium-90 Resin Selective Internal Radiation Therapy of Hepatocellular Carcinoma.

OBJECTIVE: This retrospective single-center study sought to evaluate the efficacy and safety of predictive tumor-absorbed ablative doses of Yttrium-90 resin microsphere selective internal radiation therapy (SIRT) for hepatocellular carcinoma (HCC). METHODS: We conducted a retrospective single-center study of patients with HCC treated at a tertiary referral center, who underwent Y-90 resin SIRT with ablative intent (defined as predictive tumor absorbed dose (TAD) of at least 190 Gy via planning single-photon emission computed tomography-CT dosimetry) between January 2016 and December 2023, evaluating radiological response and survival outcomes. RESULTS: Among 68 patients, median TAD was 262.24 Gy (interquartile range 209.13 Gy-336.26 Gy). Median follow-up was 1,231 days (approximately 40.4 months). At 6 and 12 months post-treatment, objective response (OR) and disease control rates (DCR) in the target tumors were 87.5% and 96.9%, and 73.6% and 86.8%, respectively, assessed with modified Response Evaluation Criteria in Solid Tumors (mRECIST) on imaging. Median target tumor time to progression (TTP) was not reached (95% CI: 785 days - not reached); portal venous invasion was an independent predictor for shorter TTP (HR 7.34, 95% CI 1.57-34.4, p  = 0.011). Median progression-free survival (PFS) was 453.0 days (95% CI, 287-577). Barcelona Clinic Liver Cancer stages B/C (HR 2.87, 95% CI 1.49-5.53, p  = 0.0016) and the absence of subsequent curative treatment (HR 2.13, 95% CI 1.10-4.12, p  = 0.026) predicted for poorer PFS. Median overall survival (OS) was 1,412 days (95% CI 596-NR). Absence of subsequent curative treatment predicted for poorer OS (HR 5.23, 95% CI 1.66-16.48, p  = 0.005). Median OS for the 190 to 300 Gy group was 699 days (95% CI 531-2,244 days), and 1,446 days (95% CI 796 days - NR) for the TAD> 300 Gy group, though observed differences in OS between the groups were not statistically significant. Two patients had possible radiation-induced liver disease, two had post-embolization syndrome, and two had radiation-induced peptic ulcer disease. These six patients were primarily responsible for the grade 2 and 3 adverse events recorded. CONCLUSION: Y-90 resin SIRT with predictive TAD of at least 190 Gy in HCC can achieve favorable 1-year target tumor disease control and a median OS of 46.4 months. Absence of subsequent curative treatment independently predicted inferior progression-free and overall survival. Among plausible reasons for the absence of a clear dose-response relationship, TAD substantially higher than 190 Gy may be required for consistent ablative efficacy.