1157P - Retreatment with peptide receptor radionuclide therapy (PRRT) in patients (p) with neuroendocrine tumors (NET): Spanish clinical experience from SEPTRALU national registry

Background

PRRT is a crucial treatment for p with somatostatin receptor-expressing NET. Strategy of re-treating with PRRT (rePRRT) to enhance clinical benefit is gaining attention. Standardized protocols for the efficacy, safety and rePRRT administration remain undefined across centers.

Methods

SEPTRALU, a Spanish national registry, comprises over 500 p with NET treated with PRRT. This study explores rePRRT instances to identify variables associated with treatment outcomes.

Results

71 rePRRT p (41% female, 55y) were included. Main primary location was ileal (35%) and pancreatic (34%), with 35% being functional. Most had hepatic (85%), bone (25%) and peritoneal (14%) metastases. Histologically, mean Ki67 was 10% with 32% Ki67 ≥10%; WHO Grade 1: 37%, G2: 49%, G3: 14%). First PRRT (PRRT1) was given as 2nd (35.5%) and 3rd line (27%). All p received 4 doses, achieving an overall response rate (ORR) of 61.7% and progression free survival (PFS) of 35 months (m). Average interval between end of PRRT1 and rePRRT was 29.3 m. For rePRRT, p received 1 to 4 doses at rates of 100%, 66%, 24% and 17%, respectively. Discontinuation was mainly due to progression (18%). ORR for rePRRT was 17.6% with a clinical benefit rate of 58.8% and PFS was not reached after 10 months of follow-up, with a 10-months PFS rate of 78%. No new toxicity alerts were reported. Univariate analysis identified predictors for rePRRT radiological response: previous PRRT1 response (p 0.004), Ki67 >30% (p 0.033) and WHO G3 (p 0.035).

Conclusions

RePRRT offers a viable therapeutic strategy for NETs, with favorable efficacy and identificable response predictors, notably prior PRRT response. Ongoing trials will yield insights into the optimal rePRRT duration and its sequencing within therapeutic algorithms.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

J. Hernando Cubero: Financial Interests, Personal, Advisory Board: Eisai, Ipsen, Novartis, AAA, Angelini, Pfizer, Roche. U. Anido Herranz: Financial Interests, Personal, Invited Speaker: Advanced Accelerator Applications, Ipsen, AstraZeneca, Merck, Pfizer, Astellas, Bayer, Eisai, BMS, Kyowa Kirin, Rovi; Financial Interests, Personal, Advisory Board: Advanced Accelerator Applications, Ipsen, AstraZeneca, Merck, Pfizer, Bayer; Financial Interests, Personal, Other, Travel expenses: Esteve. A. Garcia Alvarez: Financial Interests, Personal, Advisory Board: ADACAP (Novartis); Other, Expenses (Travel, Congress inscription): Advanz, Eisai, Ipsen, ADACAP (Novartis). All other authors have declared no conflicts of interest.