Sorbye, HalfdanHalfdanSorbyeHjortland, Geir OlavGeir OlavHjortlandVestermark, Lene WeberLene WeberVestermarkLadekarl, MortenMortenLadekarlSvensson, JohannaJohannaSvenssonSundlöv, AnnaAnnaSundlövJanson, Eva TiensuuEva TiensuuJansonGarresori, HerishHerishGarresoriHofsli, EvaEvaHofsliKersten, ChristianChristianKerstenElvebakken, HegeHegeElvebakkenPfeiffer, PerPerPfeifferMorken, SirenSirenMorkenAssmus, JorgJorgAssmusLothe, Inger Marie BowitzInger Marie BowitzLotheTabaksblat, ElizavetaElizavetaTabaksblatKnigge, UlrichUlrichKniggeCouvelard, AnneAnneCouvelardPerren, AurelAurelPerren0000-0002-6819-6092Langer, Seppo WSeppo WLanger2025-05-282025-05-282025-08https://boris-portal.unibe.ch/handle/20.500.12422/211139Background Digestive high-grade neuroendocrine neoplasms (HG-NEN) are rare and classified as neuroendocrine carcinomas (NEC) or neuroendocrine tumours G3 (NET G3), and differ in clinical and molecular characteristics, response to treatment and prognosis.Methods Prospective multicenter study registering clinical data on patients with digestive HG-NEN. Treatment outcome in patients with advanced disease was compared after centralized pathological re-evaluation.Results 427 NEC and 117 NET G3 received palliative chemotherapy. Immediate progression rate was 41% and 24%, progression-free survival (PFS) 3.4 m and 7.4 m, overall survival (OS) 7.4 m and 21.8 m for NEC and NET G3, respectively. Significant factors for OS in NEC were performance status (PS), Ki-67 > 55%, alkaline phosphatase (ALP), age, sex and for PFS colorectal primary and PS. NEC Ki-67 < 55% had similar OS comparing treatment. Significant factors for OS in NET G3 were platinum-based treatment, PS, age and ALP, and for PFS platinum-based treatment.Conclusions Survival was shorter than expected in this unique population-based cohort of advanced digestive HG-NEN, likely due to inclusion of elderly and patients with poor PS. Several novel prognostic factors were identified for NEC and NET G3. An initial sub-effective platinum-based treatment for NET G3 could not be compensated by later-line treatment.en600 - Technology::610 - Medicine & healtharticle10.48620/882834038252210.1038/s41416-025-03054-w