Evaluation of Ki67 and other predictors of survival in metastatic neuroendocrine tumor (NET) to the liver treated with Y90 radioembolization.

Abstract

e15687 Background: Ki67 index is a predictor of survival in patients with metastatic neuroendocrine tumor (NET). The purpose of this study is to evaluate Ki67 index and other potential predictors of overall survival (OS) in patients with NET metastases to the liver treated with Y90 radioembolization. Methods: In an institutional review board-approved retrospective study, consecutive patients with NET metastases to the liver who were treated with Y90 radioembolization from 2013-2018 at a single institution were evaluated. Patients with documented Ki67 index were stratified according to 2017 World Health Organization (WHO) grading based on Ki67 index (G1: < 3%, G2: 3-20%, G3: > 20%). Age, gender, and objective tumor response on post Y90 imaging were also evaluated as potential predictors of survival after Y90. Objective tumor response was evaluated at 1 and/or 3 months post Y90 with multiphase MRI utilizing Response Evaluation Criteria for Solid Tumors (RECIST). Overall survival (OS) from time of Y90 was analyzed using Kaplan-Meier estimation. Predictors of survival were evaluated using log-rank test with p < 0.05 as the statistically significant level. SPSS software v. 25 (IBM Corporation, Armonk, NY) was used for all statistical analysis. Results: A total of 77 patients were identified; 36 (47%) had a documented Ki67 index from either their primary tumor, liver metastasis, or both. Primary tumor site included pancreatic (n = 10), small bowel (n = 7), pulmonary (n = 5), gastric (n = 3), large bowel (n = 3), and renal (n = 1). A primary site was not identified in several patients (n = 7).G1 tumors comprised 31% (n = 11) of patients, while G2 and G3 tumors made up 50% (n = 18) and 19% (n = 7) of the cohort, respectively. Median overall survival (OS) of the entire cohort was 51.1 months. Median OS in patients was 63.0 months in G1 tumors, 51.1 months in G2 tumors, and 3.1 months in G3 tumors (p < 0.001). Objective response on initial MRI follow-up after Y90 radioembolization also predicted prolonged OS (51.2 months versus 17.9 months, p < 0.001). Age at time of diagnosis and gender were not predictors of survival after Y90 radioembolization. Conclusions: WHO grading based on KI67 index and objective tumor response appear to be predictors of prolonged survival in patients with metastatic NET to the liver treated with Y90 radioembolization.