Objective: Several series report on the relative contribution of ectopic ACTH syndrome (EAS) in the spectrum of Cushing's syndrome. However, prevalence of EAS in patients with thoracic or gastroenteropancreatic neuroendocrine tumors (GEP-NETs) is currently unknown. Design: We assessed, in a tertiary referral center, the prevalence of EAS in a large cohort of thoracic and GEP-NET patients including clinical, biochemical, and radiological features; management; and treatment outcome. Methods: In total, 918 patients with thoracic or GEP-NETs were studied (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012). Multiple endocrine neoplasia type 1 and small cell lung carcinoma patients were excluded. Differentiation between synchronous, metachronous, and cyclic occurrence of EAS was made. Results: Out of the 918 patients with thoracic and GEP-NETs (469 males and 449 females; median age 58.7 years (range: 17.3-87.3)), 29 patients (3.2%) had EAS (ten males and 19 females; median age 48.1 years (range: 24.7-77.9)). EAS occurred synchronously in 23 patients (79%), metachronously in four patients (14%), and cyclical in two patients (7%) respectively. NETs causing EAS included lung/bronchus (nZ9), pancreatic (nZ9), and thymic (nZ4). In four patients, the cause of EAS was unknown (nZ4). Median overall survival (OS) of non-EAS thoracic and GEP-NET patients was 61.2 months (range: 0.6-249.4). Median OS of EAS patients was 41.4 months (range: 2.2-250.9). After comparison, only the first 5-year survival was significantly shorter (PZ0.013) in EAS patients. Conclusion: Prevalence of EAS in this large cohort of patients with thoracic and GEP-NETs was 3.2%. EAS was mostly caused by thoracic and pancreatic NETs. First 5-year survival of EAS patients was shorter compared with non-EAS patients.

Radiolabeled somatostatin analog therapy can stabilize tumor growth and can be very successful in further controlling severe hypoglycemia in malignant insulinomas. In our series, this eventually resulted in improved survival outside the hospital setting.

Hypersecretion of PTHrP by metastatic GEP-NETs is very rare and seems to be exclusively associated with metastatic pancreatic NETs. PTHrP production has major clinical impact because poorly controllable hypercalcemia is associated with increased morbidity and mortality. The most successful treatment options for PTHrP-producing GEP-NETs are SSAs and PRRT using radiolabeled SSAs. Isotonic saline and bisphosphonates can be considered as supportive therapies.

An increased association between neuroendocrine tumors of the gastrointestinal tract and pancreas (GEP-NET) and other second primary malignancies has been suggested. We determined whether there is indeed an increased risk for second primary malignancies in GEP-NET patients compared with an age-and sex-matched control group of patients with identical malignancies. The series comprised 243 men and 216 women, diagnosed with a GEP-NET between 2000 and 2009 in a tertiary referral center. The timeline, before-at-after diagnosis, and the type of other malignancies were studied using person-year methodology. Poisson distributions were used for testing statistical significance. All data were cross-checked with the Dutch National Cancer Registry. Out of 459 patients with GEP-NET, 67 (13.7%) had a second primary cancer diagnosis: 25 previous cancers (5.4%), 13 synchronous cancers (2.8%), and 29 metachronous cancers (6.3%). The most common types of second primary cancer were breast cancer (nZ10), colorectal cancer (nZ8), melanoma (nZ6), and prostate cancer (nZ5). The number of patients with a cancer history was lower than expected, although not significant (nZ25 vs nZ34.5). The diagnosis of synchronous cancers, mainly colorectal tumors, was higher than expected (nZ13 vs nZ6.1, P!0.05). Metachronous tumors occurred as frequent as expected (nZ29 vs nZ25.2, NS). In conclusion, our results are in contrast to previous studies and demonstrate that only the occurrence of synchronous second primary malignancies, mainly colorectal cancers, is increased in GEP-NET patients compared with the general population.

The treatment of hormone hypersecretory syndromes caused by neuroendocrine tumors (NETs) can be a major challenge. NETs originating from the small intestine often secrete serotonin causing flushing, diarrhea and valve fibrosis, leading to dehydration or heart failure in severe cases. NETs from the pancreas can secrete a wider variety of hormones, like insulin, glucagon and gastrin leading to distinct clinical syndromes. Historically mortality in patients with functioning NETs was high due to the complications caused by the hypersecretion of hormones. This has been reduced with several drugs: protonpump inhibitors decrease acid secretion caused by gastrinomas. Somatostatin analogs can inhibit the secretion of multiple hormones and these are now the cornerstone for treating patients with a gastroenteropancreatic NET. However, peptide receptor radionuclide therapy (PRRT) with radiolabeled somatostatin analogs and everolimus can also decrease symptoms of hypersecretion and increase progression-free survival. Several factors affect the survival in patients with a functioning NET. Complications of hypersecretion negatively impact survival; however, secretion of hormones is also often a sign of a well-differentiated NET and due to the symptoms, functioning NETs can be detected in an earlier stage suggesting a positive effect on prognosis. The effect on survival is also dependent on the type of hormone being secreted. This review aims to study the effect of hormone secretion on the prognosis of NETs with the contemporary treatments options available today.