Hepatocellular carcinoma (HCC), the predominant form of primary liver cancer, is the second leading cause of cancer-related deaths across the globe. Only a small percentage of HCC patients (~20%-30%) are diagnosed at an early stage when first-line treatment options may be effective. The majority of HCC patients (>70%) are diagnosed with unresectable disease and given a poor overall prognosis. Current treatment guidelines recommend locoregional therapy with transarterial chemoembolisation (TACE) and systemic therapy with sorafenib as first-line treatment for patients with intermediate and advanced stage HCC. However, multiple factors including contraindications, technical considerations and treatment-related toxicities pose significant challenges in achieving favourable treatment outcomes, underscoring the need for a paradigm shift in managing these patients. In 2002, yttrium-90 (Y-90) resin microspheres was approved by the U.S. Food and Drug Administration (FDA) for the treatment of unresectable metastatic colorectal cancer to the liver with adjuvant floxuridine chemotherapy. However, thousands of patients with unresectable HCC have also been treated with resin Y-90. For over two decades, several small-scale prospective trials and retrospective studies have investigated and reported on the efficacy of locoregional selective internal radiation therapy (SIRT) with Y-90 microspheres in treating unresectable HCC. Although it is currently a treatment option for intermediate-stage HCC patients, mainstream clinical application of resin Y-90 has been largely limited because of the lack of sufficient clinical data from a randomised controlled trial. This could change with the imminent announcement of results from the phase 3 Sorafenib vs Radioembolization in Advanced Hepatocellular carcinoma (SARAH) trial. To provide the foundation and context for interpreting results from the SARAH trial, this article provides an overview of treatment modalities and current challenges in managing unresectable HCC. There is also a review of key prospective and retrospective studies evaluating the use of Y-90 SIRT, specifically Y-90 resin microspheres in unresectable HCC, which led to the development of the SARAH trial.

Methods: To identify relevant publications, the PubMed database was queried using one or more of the following search terms alone or in combination with Boolean operators: epidemiology, hepatocellular, hepatocellular cancer, hepatocellular carcinoma, unresectable, radioembolisation, selective internal radiation therapy, SIR-Spheres, yttrium 90, TACE, and sorafenib. The results were sorted or filtered by "Author", "Publication dates" or "Article types" to identify articles relevant to each section of the review. To ensure that information on ongoing clinical trials involving Y-90 resin was included, we conducted a search on "ClinicalTrials.gov", by combining the search terms "HCC" OR "hepatocellular carcinoma" with "Y 90" OR "yttrium 90" OR "radioembo", and screened for studies that involved treatment with Y-90 resin microspheres.