Prevalence of second primary malignancies in patients with well-differentiated neuroendocrine tumors.

Objectives: Neuroendocrine tumors (NETs) constitute a diverse group of tumors. NETs are often diagnosed late, due to nonspecific symptoms. Second Primary Malignancies (SPMs) have been reported in up to 25% of NETs and their incidence has been described as negative predictor of OS. We aimed to assess the prevalence of SPMs in patients with NETs treated at a specialized center.

Methods: We conducted a retrospective analysis of patients with metastatic well-differentiated gastro-entero-pancreatic NETs and lung carcinoids treated with Somatostatin Analogs between 2017 and 2019. Control group patients with hormonally inactive pituitary lesions and microprolactinomas hospitalized between 2016 and 2019 were included.

Results: 135 patients (85 women, 50 men) with NETs were enrolled. SPMs were more common in NETs compared to control group (p=0.029). Twenty-six SPMs were diagnosed in 24 patients (17.8%). The control group comprised 94 patients, among whom 7 patients (7.7%) developed SPMs. Mean(SD) age at the end of follow-up was 64.8(10.2) years, with duration from NETs diagnosis to the end of follow-up of 5.3(3.8) years.

Conclusions: The risk of SPMs is high in NETs, with multiple neoplasms diagnosed in over one-sixth of patients. Active surveillance for SPMs is strongly indicated and should be integral to the follow-up of NETs.