Peptide receptor radionuclide therapy (Lu-177 PRRT) in neuroendocrine tumors (NET): Single institution experience over 15 years.

Abstract

e16343 Background: Peptide receptor radionuclide therapy (PRRT) is one of the standard treatments for unresectable or metastatic neuroendocrine tumors (NETs). Treatment with Lu177-Dotatate PRRT therapy results in superior progression-free survival and overall survival and a significantly higher response rate than high-dose octreotide LAR.This study aims to report the efficacy of PRRT in NET cases treated at King Faisal Specialist Hospital and Research Center (KFSHRC) in Saudi Arabia. Methods: This retrospective analysis included patients with unresectable, well-differentiated NETs who received PRRT between 2008 and 2022. Demographic, clinical, and tumor characteristics were collected, including primary tumor site, WHO grade, Ki67 index, and ECOG performance status. Objective response rate (ORR), Progression-free survival (PFS), and overall survival (OS) were assessed. Univariate analysis was performed to evaluate correlations between clinical variables and treatment outcomes. Results: A total of 55 patients received PRRT, with a median age of 44 years (range: 18–75). Tumor grading was distributed as follows: 36 patients (65.4%) had WHO Grade 2 tumors, 15 patients (27.3%) had Grade 1 tumors, and 4 patients (7.3%) had Grade 3 tumors. The primary tumor sites were the small intestine in 21 patients (38.2%), the pancreas in 17 patients (30.9%), and other locations in 17 patients (30.9%). Functional tumors were identified in 29 patients (52.7%). Regarding treatment sequencing, PRRT was administered as first-line therapy following somatostatin analogs (SSAs) in 37 patients (67.3%), while 18 patients (32.7%) received it after multiple prior treatments. Twenty-one patients (38.2%) achieved partial response, 23 patients (41.8%) had stable disease, and 10 patients (18.2%) experienced progression. At a median follow-up of 38 months,20 patients (36.4%) were dead, and 10 patients (18.2%) were alive with no disease. The 5-year OS rate was 61.2%, with a median OS of 76.1 months. The 5-year PFS rate was 15.1%, with a median PFS (mPFS) of 18.4 months. Univariate analysis showed no significant differences in mPFS based on WHO grade: 18.4 months for Grade 1, 13.3 months for Grade 2, and 26.3 months for Grade 3. Similarly, no significant differences were observed in mPFS based on primary tumor site, Ki67 index, or Dotatate SUV. Conclusions: Lu177-Dotatate PRRT is an effective treatment for well-differentiated NETs, demonstrating consistent efficacy across various subgroups, regardless of WHO grade, Ki67 index, or primary tumor site. This study, conducted at a single institution in Saudi Arabia, reinforces the role of PRRT in improving survival outcomes for NET patients, both as a first-line option after SSA therapy and in later lines of treatment. Results align with international data, supporting its broad applicability.