Epidemiology and Management of Neuroendocrine Neoplasms of Unknown Primary in Switzerland

Abstract Background Neuroendocrine neoplasms (NEN) are mainly located in the gastrointestinal tract or the lungs. In up to 14%, the primary tumor remains unidentified, classified as cancer of unknown primary (CUP). Due to their rarity and heterogeneity, CUPs are poorly studied. Methods Retrospective data analyses with data provided by the SwissNET registry from 2008-2022 including patients diagnosed with CUP or metastasised NEN with known primary (mNEN). Main objective was to assess the demographics, tumor characteristics and the diagnosis and treatment of CUPs in comparison to mNEN. Secondary objective was to evaluate overall survival of CUPs in general and compared to mNEN using propensity score matching. Results 207 CUP and 437 mNEN patients were included. Prevalence was slightly higher in men (54.6% and 57.9%, respectively). Median (IQR) age at diagnosis was higher for patients with a CUP (67.7 years (59.0, 77.2)) compared to mNEN (62.9 years (53.5, 71.5), p Conclusion Overall survival time of patients with CUPs was shorter compared to mNEN, possibly due to the higher-grade tumors at diagnosis.