90Y Radioembolization for Metastatic Neuroendocrine Liver Tumors : Preliminary Results From a Multi-institutional Experience

Minimally invasive therapies such as transarterial chemoembolization and radiofrequency ablation are used for hepatic metastatic neuroendocrine tumor (NET) therapy. Results from another minimally invasive therapy, radioembolization, remain unknown. The purpose of this multicenter open label phase II study was to assess the efficacy and safety of yttrium-90 (Y) radioembolization for treating hepatic metastatic NET using a primary outcome of tumor response and secondary outcomes of serologic toxicities and survival. In this multicenter study, all patients underwent lobar radioembolization using glass or resin Y radioembolic agents. Patients were assessed serologically and radiographically at 2 to 4 weeks and then at 1 to 3 month intervals after treatment. We 1) compared liver volumes, radiation doses, and serologic liver function tests (unpaired t test, P = 0.05) and 2) assessed tumor response, serologic toxicity, and median survival from first Y therapy. The clinicaltrials.gov identifier was NCT00532740. Forty-two patients underwent radioembolization using glass (mean age 58 +/- 12 years) or resin (mean age 61 +/- 11 years) microspheres. A statistically significant greater median radiation dose was delivered to each lobe using glass (right lobe 117 Gy; left lobe 108 Gy) than using resin (right 50.8 Gy; left 44.5 Gy) (P < 0.01). Using Response Criteria in Solid Tumors, 92% of glass and 94% of resin patients were classified as partial response or stable disease at 6 months after treatment. Six patients experienced grade 3/4 toxicities during the follow-up period. Median survival was 22 months (glass) and 28 months (resin) (P = 0.82). Y radioembolization of metastatic NET is a viable therapy with acceptable toxicity. Further investigation is warranted.