Background: PRRT, licensed for gastroenteropancreatic (GEP) NETs, has been used with somatostatin analogs such as lanreotide depot (LAN). PRELUDE is the first retrospective study to describe use of LAN with PRRT (LAN–PRRT) in advanced NETs. Methods: PRELUDE was an international, retrospective, non-comparative analysis of medical records of patients receiving LAN with ¹⁷⁷Lu-DOTATATE/DOTATOC, and 12 mo LAN only follow-up. Key inclusion criteria: metastatic/locally advanced, grade 1/2, somatostatin receptor positive GEP or lung NET, progressive disease (PD) in the year prior to LAN–PRRT start, ≥1 LAN injection 8 wks before the 1^st LAN–PRRT cycle, continuous LAN use during LAN–PRRT, cumulative PRRT activity ≥500 mCi. Primary endpoint: progression-free survival (PFS) rate from day 1 of 1^st cycle to the end of the last LAN–PRRT cycle (RECISTv1.1, centrally assessed). Secondary endpoints included best overall response (OR; RECISTv1.1), objective response rate (ORR), change from baseline in diarrhea and flushing. Safety included incidence of nephro, hemato and hepatotoxicity; vomiting during infusion. Results: Enrollment was terminated early (insufficient recruitment). Of 40 patients enrolled, 39 had GEP NET (incl.; ileum 33.3%, unknown origin 25.6%, right colon 20.5%, pancreas 10.3%); one had lung NET (full analysis set: GEP NET n = 23, lung NET n = 1). Most patients with GEP NET had Ki67 > 2–≤20% (53.1%), global overall Krenning score (centrally assessed) grade 4 (70.4%), received 4 (17/23 patients) LAN–PRRT cycles, and 120mg LAN (18/23) last dose before PRRT. Median (range) LAN exposure: 37.0 (13.2, 90.0) mo overall; 12.6 (6.1, 32.5) mo during LAN only follow-up. PFS rate [95% CI]: 91.7% [53.9–98.8]. Best OR (GEP NET): 34.8% partial response, 60.9% stable disease, 4.3% PD. ORR at time of last LAN–PRRT cycle [95% CI]: 27.3% [13.2; 48.2]. Most patients with GEP NET had stable/improved diarrhea (15/15) and flushing (13/14). Few toxicities reported; no safety issues identified. Conclusions: Effectiveness data were encouraging in this selected population. In clinical practice, LAN use is considered before, during, and after PRRT. Clinical trial information: NCT02788578