Q. How common are NETs?
A. NETs are more prevalent than stomach and pancreatic cancers combined.1,2 Surveillance, Epidemiology, and End Results (SEER) Program data from 1973 to 2004 indicate that the annual incidence of NETs has increased 5-fold to an estimated 5.25/100,000.1 And, the incidence of NETs is predicted to continue rising.3 Prevalence is also high.1
Q. How are NETs detected?
A. NETs can form in multiple locations throughout the body,3 and although they share a number of common features, their clinical presentation may vary according to site of origin, secretory potential, and histologic subtype.4 Some patients may be asymptomatic or present episodically with nonspecific symptoms, while other patients may present with a syndrome or symptoms that warrant further investigation.5 A number of imaging techniques and serum biochemical tests can be used to build the case for a NET diagnosis.
Q. What are the clinical characteristics of NETs?
A. The key clinical characteristics of NETs are
- Size: Primary NETs are usually small tumors that are often (but not always) slow-growing.1,4 Even small gastrointestinal and pancreatic NETs (<2 cm) can be aggressive and metastasize5-7
- Varied clinical presentation: NETs may be silent for years, or produce vague symptoms that are easily mistaken for other conditions. Depending on type of NET, these symptoms can include diarrhea, abdominal pain, flushing, and hypoglycemia4
- Late appearance of secretory symptoms: NETs usually metastasize to liver and bone before becoming symptomatic4
Q. How serious are NETs?
A. NETs are cancerous tumors with malignant potential. Even small NETs (<2 cm) can metastasize.5-7 An analysis of long-term SEER data from 1973 to 2004 showed that 50% of all patients with reported disease stage have either regional or distant metastases at diagnosis,1 and patients with distant metastases (well- and moderately differentiated NETs) have a median survival of 33 months.1 The prognosis for patients with metastatic NETs is dependent on tumor grade. For patients with well- and moderately differentiated metastatic NETs, the 5-year survival rate is 35%.1 For patients with poorly differentiated NETs with distant metastases, the 5-year survival rate is 4%.1
Q. Where in the body do most NETs occur?
A. The majority of NETs originate in the gastrointestinal tract or pancreas,1 and are collectively referred to as gastroenteropancreatic NETs (GEP-NETs). NETs can be further delineated by the embryonic origin of the transformed cell line: foregut (respiratory tract, thymus, stomach, duodenum, pancreas), midgut (small intestine, appendix, ascending colon), and hindgut (transverse colon, descending colon, rectum).8,9 NETs that are not gastrointestinal or pancreatic in origin can arise in the respiratory tract, ovaries, and testes, as well as in other endocrine tissue (eg, thymus, adrenal gland).3
Q. How are NETs managed?
A. Management depends on the type of NET, its size and location, and associated symptoms. Among the options that may be considered are10
- Observation
- Surgery to reduce tumor burden or with curative intent for localized NETs
- Targeted medical therapy, biotherapy, or chemotherapy
- Radiofrequency ablation and chemoembolization to reduce or eliminate hepatic metastases
NETs are complicated and may involve different comorbidities; experts recommend management by specialists using a multidisciplinary approach.10,11
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