Optimization of Radioembolic Effect with Extended-shelf-life Yttrium-90 Microspheres: Results from a Pilot Study

Purpose: To evaluate the safety and efficacy of yttrium-90 (⁹⁰Y) radioembolization with extended-shelf-life glass microspheres. We postulated that this approach, for the same planned tissue dose of 120 Gy, would increase the embolic load, improve distribution, and result in enhanced tumor response without causing additional adverse events. Materials and Methods: Between June 2007 and September 2008, 50 patients with extensive tumor burden and/or markedly hypervascular tumors (13 hepatocellular carcinomas, and 37 liver metastases) underwent radioembolization with extended-shelf-life microspheres at a planned dose of 120 Gy. Baseline and follow-up imaging and laboratory data were obtained. Response in the target lesion was assessed with cross-sectional imaging by using World Health Organization (WHO) and European Association for the Study of the Liver (EASL) guidelines. Results: The mean delivered radiation dose was 126 Gy. The mean increase in embolic load with this approach was 111%, corresponding to an increase from 3.6 to 7.3 million microspheres. Clinical toxicities included fatigue (28 patients, 56%), abdominal pain (19 patients, 38%), and nausea/vomiting (six patients, 12%). Grade 3-4 bilirubin toxicity was seen in one patient. Two gastroduodenal ulcers were observed. With cross-sectional imaging, response rates according to WHO and EASL guidelines were 51% and 69%, respectively. Conclusions: The results demonstrate the safety and efficacy of extended-shelf-life ⁹⁰Y glass microspheres. The increased embolic load and lowered activity per microsphere theoretically resulted in better tumor coverage and, hence, improved response rates. This standardizable treatment paradigm provides a minimally embolic therapy for liver tumors.