Endocrine Abstracts

Background: 177Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) is approved for treatment of metastatic gastroenteropancreatic (GEP) neuroendocrine tumors (NETs). Here we report our single institution experience with PRRT.

Methods: A retrospective review of patients who received ¹⁷⁷Lu-DOTATATE at our institution was performed. Demographics, clinical and laboratory values, and post-treatment outcomes were reviewed. RECIST 1.1 and CTCAE version 5.0 guidelines were used to evaluate radiographic response and grade treatment toxicities respectively.

Results: Between 2018 and 2024, 195 patients were treated with ¹⁷⁷Lu-DOTATATE. Median follow-up was 21 months. Breakdown of primary site and grading of NETs are provided in Table 1. The median and mean SUVmax of the hottest lesion on DOTATATE-PET was 41.9 and 51.5 (IQR 28.3-60.3). 106 (54%) patients had non-functional tumors. In terms of marrow toxicity, the WBC decreased by 29%±28%, platelets by 36%±27% and hemoglobin by 11%±12% during treatment. eGFR fell by an average of 7%±28% at any point in time after treatment. G3/4 anemia was observed in 10/195 (5%), G3/G4 thrombocytopenia in 6/195 (3%), 8/195 (4%) patients developed G3/G4 leukopenia. Also 7/195 (4%) patients developed G3/G4 ascites and 2/195 (1%) developed AML (1 G4 and 1 G5). 142 (72%) patients were kept on SSAs after PRRT. 19 (10%) patients were re-treated. In terms of efficacy, and radiographic response: 1 (0.5%) CR, 64 (33%) PR, 106 (54%) SD, and 15 (8%) PD. Median PFS (mPFS) for SBNET was 32 (23-38) months, mPFS for PNET was 19 (14-27) months, and mPFS for patients with other/unknown primary tumor was 27 (18-40) months, P = 0.02. By grade, the mPFS for G1 was 42 (25-52) months, G2 26 (21-32) months and G3 14 (12-20) months, P <0.001. Also, the mPFS for patients ³ 70 years old was 28 (19-38) months, and for patients < 70 years old was 24 (20-31) months P = 0.459.

Conclusions: Our results mirror published results, with shorter PFS in patients with higher grade disease, and PNET compared to SBNET. Older patients had a similar PFS compared to younger patients overall. The most common toxicity was marrow toxicity, and two patients developed AML after treatment.

ABSTRACT ID28667