Y-90 Radioembolization For Neuroendocrine Cancers Liver Metastases Provides Sustained Therapeutic Effect With Minimal Toxicity

343 Background: Radioembolization (RE) is the delivery of radioactive microspheres (90Y) via the hepatic artery, which permanently implant preferentially in metastatic lesions, sparing adjacent normal liver. Metastatic neuroendocrine tumors in the liver are a common clinical problem which can be treated with RE. It is an outpatient procedure performed with increasing frequency worldwide for a variety of solid tumor types. Methods: A single institution retrospective review of all neuroendocrine patients treated with radioactive resin microspheres to control hepatic metastases. Details reviewed included: specifics of treatment and delivery, RECIST response at 3 and 6 months, acute and delayed radiation toxicities by CTC3ae, and analyses of tumor and radiation factors related to response and liver control. Results: A total of 56 patients; 26 male, 30 female, received a total of 85 separate treatments with resin 90Y microspheres. Treatment volume was all hepatic tumors with each treatment, usually selective whole liver in one fraction. Whole liver in 1 treatment comprised 86%, right lobe only in 10% and left lobe in 4%. Thirty-six patients (64.3%) received 1 treatment, 12 patients 2 fractions, 7 patients 3 fractions, and 1 patient 4 fractions. The median activity of 90Y delivered was 1.49 GBq (0.35 – 2.9 GBq). BSA approach was used for pretreatment activity calculations for all patients, with median of 100% planned activity delivered (26% - 147%). No grade 4 toxicities occurred, and only two grade 3 events were found (gastric ulcers). The median follow up is 24.2 mo. (1 – 93.4 mo.). RECIST at 3 and 6 months: CR 6.5%, SD 49.1%, PR 42.6% and PD 1.6%. Delivered activity (GBq) was associated with PR at 3 months (p=0.07, two-tailed t-test). Conclusions: Our experience is consistent with other published reports confirming the efficacy and low toxicity of this liver-directed ablative approach for unresectable neuroendocrine carcinomas. Multiple treatments to the whole liver were well tolerated. The BSA method of pretreatment radioactivity estimation is useful and safe in this tumor type.