Abstract Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant tumor predisposition syndrome in which neuroendocrine tumors (NET) represent a major driver of morbidity and mortality. Timely recognition of MEN1 after NET diagnosis enables syndrome‐specific surveillance and cascade testing, yet real‐world evidence on MEN1 testing implementation in oncology pathways remains limited. The aim of this study was to evaluate MEN1 testing practices and assess concordance with guideline‐based indications and nomogram‐predicted risk. A retrospective cohort study was performed within NETwerk, a Belgian ENETS CoE, with patients <70 years diagnosed between 2012 and 2024 with pancreatic, pulmonary, gastric, or thymic well‐differentiated NET. MEN1 testing data were extracted from medical records. In patients without a prior MEN1 diagnosis at NET presentation, guideline‐based indications for MEN1 testing were assessed and compared with observed testing. Additionally, nomogram‐predicted MEN1 risk was estimated, using a ≥5% threshold for descriptive risk stratification, and overlap between guideline‐ and nomogram‐based indications was described. In 267 patients without prior MEN1 diagnosis, MEN1 testing was performed in 42 (15.7%), mainly in patients ≤50 years. Including 21 patients with MEN1 diagnosis before NET development, overall MEN1 prevalence was 10.4%. In patients without a prior MEN1 diagnosis at NET presentation, guideline‐based indications showed moderate agreement with observed testing ( κ = 0.50, p < .001) without directional bias toward over‐ or undertesting, with undertesting most evident in MEN1‐suspicious tumor presentations (gastrinoma, early‐onset panNET, thymic NET). Among patients tested despite lacking guideline indications ( n = 20), none had MEN1. Application of the nomogram yielded an exact risk score for 77 patients and a risk score range for the remaining 190 patients due to incomplete phenotyping. In the patients with complete phenotyping, median predicted MEN1 risk was 3.3% (IQR 2.4–4.3). Testing rate increased with higher predicted risk: 85.7% (12/14) for ≥5% underwent testing vs. 23.8% (15/63) for <5%. Guideline‐ and nomogram‐based stratification overlapped in most patients. In conclusion, this retrospective cohort study shows that MEN1 testing after NET diagnosis showed moderate alignment with guideline‐based indications and was constrained by incomplete risk capture and phenotyping. Embedding a standardized MEN1 risk checklist and minimal endocrine phenotyping into NET MDT workflows, supported by quantitative risk estimation in selected cases, may improve guideline‐concordant MEN1 detection and downstream benefits for patients and their relatives.
Mariën et al. (Fri,) studied this question.