2 Hospital Physician Board Review Manual www.turner-white.com
Management of Gastroenteropancreatic
Jennifer A. Chan, MD, MPH, and Matthew H. Kulke, MD, MMSc
Neuroendocrine tumors (NETs) are a rare, heterogeneous group of neoplasms that arise from
neuroendocrine cells located throughout the body.
These tumors are characterized by variable but
most often indolent biologic behavior. They are
also classically characterized by their ability to
secrete peptides, resulting in distinctive hormonal
syndromes. Although NETs have been considered
rare, recent studies suggest that they are more
common than previously suspected. An analysis
of the Surveillance, Epidemiology, and End Results (SEER) database demonstrated a significant
increase in the incidence of NETs over time with
an age-adjusted annual incidence in the United
States of 5.25 cases per 100,000 population. 1
The increase in incidence is likely attributable to
increasing awareness, improved diagnostic strategies, and possibly other undetermined environmental and genetic factors.
When NETs are diagnosed at an early stage,
surgical resection is often curative. Unfortunately,
curative surgery is rarely an option for patients with
metastatic disease, and standard cytotoxic therapy
for patients offers limited benefit. Treatment ap-
proaches with targeted therapy, including the use
of agents targeting the vascular endothelial growth
factor (VEGF) signaling pathway, the mammalian
target of rapamycin (mTOR), and other pathways
involved in neuroendocrine tumorigenesis, pro-
vide new therapeutic options for these patients.
The aim of this review is to summarize advances
in the diagnosis and management of well-differen-
tiated, low-grade gastroenteropancreatic neuroen-
docrine tumors (GEP NETs). The management of
poorly differentiated neuroendocrine carcinomas
and mixed exocrine-endocrine tumors is beyond
the scope of this review.
NETs arising at different sites within the body are
classified according to their histologic features. A
number of histologic and anatomic classification
systems have been proposed to describe these
tumors (Table 1).2–4 Although there are differences
in the specific criteria for grading tumors, the clas-
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