CIO 2021-15 Long-Term Outcomes Following Y90 Radioembolization of Neuroendocrine Liver Metastases

Purpose: 90Y radioembolization has been studied as an effective therapy for neuroendocrine liver metastases (NELM). We aim to further characterize treatment outcomes as it relates to the primary lesion location.

Material and Methods: 170 patients (74 women/96 men) with NELM were enrolled in the Radiation-Emitting SIR-Spheres in Non-Resectable liver tumor (RESiN) registry (NCT 02685631). Before 90Y, 23 (14%) patients had undergone hepatic resection, 118 (83%) were on octreotide, and 47 (33%), and 57 (40%) received biologic or cytotoxic therapy. 62 patients (36%) had undergone previous arterial embolization. 76 patients had extrahepatic disease at presentation. 76 patients were ECOG 0 and 86 ECOG 1 or more. Tumor grade was known in 81 (48%) of patients: 57 were well-, 12 moderate- and 12 poorly differentiated. Kaplan-Meier analysis and log rank tests were performed to compare overall survival (OS) by tumor location including foregut (FG, n=39), midgut (MG, n=54), hindgut (HG, n=10), pancreas (P, n=36) and unknown (U, n=13). Toxicities were reported using Common Terminology Criteria for Adverse Events v.5.

Results: 80 patients (47%) underwent bilobar treatment and 90 (53%) had unilobar. Median tumor burden was 26% (IQR: 11.8-49.7). Median prescribed activity was 1.3 GBq (IQR: 0.9-1.5 GBq) and 1.9 GBq (IQR: 1.6-2.2 GBq) for uni- and bilobar treatments. 1, 2, and 3-year OS was 75%, 61% and 44%. Median OS was 30 months. The longest OS was in patients with pancreas and hindgut tumors (42 and 41 months, respectively) while the shortest OS was in foregut primaries (25 months). This difference was not statistically significant (X2=6.1, p=0.2). Well-differentiated tumors had a median OS of 35 months, compared to 13 and 25 months for moderate and poorly differentiated tumors. PFS for the entire group was 25 months with 1, 2, and 3-year PFS of 70%, 53%, and 34%. There were no grade 4 or 5 toxicities, and the most common grade 3 toxicities were bilirubin increase (n=10, 5.9%) and new ascites (n=3, 1.8%).

Conclusions: In a heavily pre-treated population with a high incidence of extrahepatic disease and limited performance status, 90Y was effective and safe in treatment of NELM, with median OS of 35 months for well differentiated tumors. Grade 3 or greater hepatic toxicity was identified in <6% of patients.