Background: The prognosis of patients with hepatic metastases from neuroendocrine tumors (NET) is generally good, and radioembolization with Yttrium-90 microspheres is a locoregional therapy that is used in efforts to improve hepatic disease control and survival. This study aims to describe the survival outcomes and toxicities associated with radioembolization for hepatic-predominant metastatic NET in a large singleinstitution cohort. Methods: A total of 59 patients underwent radioembolization for metastatic NET with hepatic predominant disease at a single academic center. Patient outcomes were analyzed by Kaplan-Meier survival analysis and toxicities were detailed and described. Ten patients within the cohort underwent post-treatment dosimetric analysis using PET-MRI and normal liver dosimetry was correlated with hepatic fibrosis and toxicity. Results: Median overall survival from time of radioembolization in the patient cohort was 31 months, and the 1-and 2-year overall survival was 80.4% and 65.6% respectively. Median hepatic progressionfree survival and overall progression-free survival were 18 and 13 months, respectively. Three patients died of hepatic failure that was possibly therapy-related. Ten patients underwent evaluation of post-treatment dosimetry following radioembolization. In patients who did not develop hepatotoxicity or hepatic fibrosis, mean dose to normal liver was 25.4 Gy, while the mean liver dose in patients who experienced toxicity (hepatic fibrosis in n=2 and death from hepatic failure in n=1) was 59.1 Gy. Conclusions: Overall survival following radioembolization for hepatic metastases from NET is excellent; however, deaths that are potentially treatment-related have been observed. Preliminary data regarding dose to normal liver is suggestive of a relation between dosimetry and toxicity, however further work is required to further elucidate the mechanism, correlation with dosimetry, as well as additional patient and tumor factors that may predispose these patients to toxicity.

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Purpose: To determine prevalence of hepatobiliary infections following Yttrium-90 (Y-90) radioembolization in patients with liver malignancy and a history of biliary instrumentation. Materials: Records of 80 patients (median age 64 years, 50 men) with primary (n¼28) or metastatic (n¼52) cancer of the liver and a history of biliary-enteric anastomosis (n¼34), sphincterotomy (n¼13), or indwelling biliary stent (n¼28) or drain (n¼2) across the ampula of Vater, who underwent 110 Y-90 radioembolization procedures with resin or glass microspheres at 10 highvolume centers between 2005 and 2015 were retrospectively reviewed. Data regarding previous liver-directed and systemic therapy, performance status, liver function, Y-90 dosimetry, antibiotic and bowel preparation prophylaxis were collected. The primary outcome was development of hepatobiliary infection. Univariate and multivariate analyses were performed using generalized estimating equation method. Results: Hepatobiliary infections (liver abscesses in 8 patients, cholangitis in 4 patients) developed following 9 (8.2%) radioembolization procedures in 9 (11%) patients. Eight patients required at least one hospitalization (range 1-7 per patient), spent a median of 13 days (range 2-113 days) in a hospital for treatment of the infection, and required invasive treatments including percutaneous abscess drainage (n¼7), endoscopic retrograde cholangiography with stenting and removal of stones (n¼3), or insertion of percutaneous biliary drains (n¼1). Infections resolved in 4 patients, 2 patients died as a result of the infection, and 3 patients are continuing to receive broad-spectrum antibiotic therapy. Younger age (p¼0.01), higher baseline aspartate aminotransferase (AST) level (p¼0.04), larger target liver volume (p¼0.02), and a higher delivered Y-90 activity (p¼0.03) were associated with a higher risk of infection. Antibiotic prophylaxis and bowel preparation were not protective against infection. Conclusions: Liver abscess and cholangitis are uncommon but morbid and difficult to manage complications of Y-90 radioembolization in patients with a history of biliary instrumentation.