Repeat Peptide Receptor Radionuclide Therapy in Neuroendocrine Tumors: A NET Center of Excellence Experience.

Abstract

Introduction: The available data for the safety and efficacy of repeat peptide receptor radionuclide therapy (PRRT) are almost exclusively from European centers. We present an updated experience with repeat PRRT in a cohort of US patients with neuroendocrine tumors (NETs) at our NET center of excellence.

Methods: We used our single-center longitudinal NET registry to identify patients who had been previously treated with at least one dose of PRRT (PRRT 1, either ¹⁷⁷Lu DOTATATE or ⁹⁰Y DOTATOC) and following radiographic disease progression were re-treated with a second course of PRRT (PRRT 2). We reviewed patient, tumor and treatment characteristics, objective response rates, and toxicities after PRRT 1 and PRRT 2.

Results: A total of 11 patients were included in the analysis. 45.5% (5/11) of patients received ¹⁷⁷Lu DOTATATE PRRT only, both for PRRT1 and PRRT 2, while 54.5% (6/11) of patients received ⁹⁰Y DOTATOC PRRT for PRRT1. At first restaging scan after PRRT2 (3-6 months), 18.2% (2/11), 36.4% (4/11), and 27.3% (3/11) of patients had PR, SD, and PD, respectively; 2/11 patients (18.2%) died before the first restaging scan. Therefore, 5/11 (45.5%) patients were noted to have disease progression. Median PFS for PRRT1 was 25.4 months and median PFS for PRRT2 was 13.1 months (p = 0.0001). We did not find a statistically significant difference between the occurrence of short and long-term hematological toxicities as well as renal toxicity after PRRT1 and PRRT2.

Conclusion: We show that repeat PRRT may benefit select patients and have an acceptable safety profile. In our cohort, PFS was significantly lower after PRRT2 as compared to PRRT1.