Background. The incidence of secondary malignancies is increased in patients with malignant and premalignant conditions. Although neuroendocrine tumors (NET) are uncommon, their incidence is increasing. We evaluated the rate of additional malignancies in patients with NET. Methods. Using the Surveillance, Epidemiology, and End Results (SEER) database, we identified a cohort of patients with pancreatic NET (PNET) or gastrointestinal NET (GINET). We determined the incidence of additional cancers diagnosed either before or after the diagnosis of PNET or GINET, by comparing these rates with the general population. Using multivariable regression, we evaluated factors that increased the risk of an additional malignancy. Results. A cohort of 9,727 NET patients was identified. A total of 3,086 additional cancers occurred in 2,508 patients (25.8%). The most common sites of additional malignancies included colorectal (21.1%), prostate (14.5%), breast (13.3%), and lung (11.6%). Among patients with PNET, the incidence of breast, lung, uterine, lymph, and pancreatic cancers was less than expected in the general population, whereas in patients with GINET, the observed incidence of nearly all malignancies exceeded that expected. Increasing age, marital status, and localized NET were associated with increased risk.
Conclusion. Our study shows that the incidence of additional malignancies in patients with PNET and GINET is 25.8%. Patients with GINET are at increased risk of additional malignancies, whereas patients with PNET have a decreased risk compared with the general population. More vigilant surveillance for secondary malignancies should be performed in patients with GINET. Studies investigating potential etiologic oncogenic pathways are warranted.
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