Evolution of Radioembolization for Hepatocellular Carcinoma: From First Commercial Use through the State of the Art

Abstract In the 25 years since it became commercially available, yttrium 90 transarterial radioembolization has become a dominant arterial treatment modality for all stages of hepatocellular carcinoma (HCC). With lower toxicity and better, more durable oncologic outcomes than chemoembolization, radioembolization has evolved from a bail-out option in advanced disease to a disruptive competitor of percutaneous ablation and an accepted part of the Barcelona Clinic's stage-based treatment guidelines. Lobar dosimetry has evolved from single to multi-compartment models with patient-specific tumor and normal tissue dose optimization leveraging dedicated software. Radiation segmentectomy has proven safer and more effective than lobar treatment for localized HCC by sparing the majority of liver tissue any radiation exposure whatsoever. Continuing improvements in microcatheter technology and in three-dimensional angiographic image guidance and volumetry will continue to make mapping, dosing, and treating more efficient. More complete understanding of the interplay between tumor dose, tumor coverage, sphere count, and sphere radioactivity will drive routine outcomes closer to durable 100% tumor necrosis. With an eye toward the central role of dosimetry, this review aims to highlight the marquee studies leading to the current state of the art and laying the ground for radioembolization treatments of the future.