Somatostatin Analogues Do Not Improve Survival in Grade 3 Gastroenteropancreatic Neuroendocrine Neoplasms: A Registry-Based Analysis with Ki-67 Stratification

Background/Objectives: The efficacy of somatostatin analogues (SSA) in Grade 3 (G3) neuroendocrine neoplasms (NEN) remains controversial, and registry data rarely permit a formal separation of NET G3 from neuroendocrine carcinoma (NEC).

Methods

We analyzed 519 patients with G3 gastroenteropancreatic (GEP) NEN recorded in a national neuroendocrine tumor registry (data export 3 April 2025; 464 de novo G3, 55 transformed G3); bronchopulmonary primaries were excluded. A Ki-67 > 55%, entered as a time-varying indicator, served as a surrogate for NEC. Outcomes were compared using Kaplan–Meier and Cox proportional hazards models with all treatments and the Ki-67 > 55% indicator entered as time-varying covariates.