Abstract Purpose PRELUDE aimed to assess use and effectiveness/safety of lanreotide autogel/depot (LAN) combined with ¹⁷⁷Lu-DOTATOC or ¹⁷⁷Lu-DOTATATE (LAN–peptide receptor radionuclide therapy [PRRT]) in patients with progressive neuroendocrine tumours (NETs). Methods International, non-interventional, retrospective, non-comparative analysis of medical records from patients with progressive metastatic or locally advanced grade 1 or 2 gastroenteropancreatic (GEP)- or lung-NETs. The primary endpoint was progression-free survival (PFS) at end of last LAN–PRRT cycle. Secondary endpoints included PFS at last available follow-up, best overall response, objective response rate (ORR), presence and severity of diarrhoea and flushing, and safety. Post-hoc analyses were conducted to determine pre-treatment tumour growth rate (TGR) cutoffs that best predicted the ORR during treatment. Results Forty patients were enrolled (GEP-NETs, n = 39; lung-NETs, n = 1). PFS rates were 91.7% at end of last LAN–PRRT cycle and 95.0% at last available follow-up. In the full analysis set, best overall response among patients with GEP-NETs (n = 23) was stable disease (n = 14, 60.9%), partial response (n = 8, 34.8%) and progressive disease (n = 1, 4.3%). The ORR was 27.3% at end of last LAN–PRRT cycle and 36.8% at last available follow-up. Optimal baseline TGR cutoffs for predicting ORR at these time points were 1.18% and 0.33%, respectively. At baseline, 81.0% of patients had diarrhoea or flushing; both remained stable or improved in most cases. No increased adverse drug reactions were reported. Conclusion Despite the major recruitment shortfall for the PRELUDE study, effectiveness data were encouraging in this selected population, highlighting the potential usefulness and feasibility of LAN combined with and after PRRT in patients with GEP-NETs. The study also identified challenges associated with evaluating clinical practice in a rare-disease setting and highlighted the need for standardisation of PRRT procedures. Trial registration Trial number: NCT02788578; URL: https://clinicaltrials.gov/ct2/show/NCT02788578