Neuroendocrine Tumors in the Liver
(Carcinoid and Others)
Islet cell carcinoma and carcinoid tumors are rare and account for
less than 1% of all malignant disorders in the United States. It is estimated that fewer
than 2000 new cases occur in the United Sates each year. Compared with more common
malignant disorders, these have an indolent natural history and can secrete peptides,
resulting in devastating clinical syndromes. Aggressive therapy is recommended to palliate
moderate symptoms or to avert impending hepatic compromise.
Hepatic metastases from carcinoid tumor or islet cell carcinoma are
frequently hypervascular because they derive their blood supply predominantly from the
hepatic artery; thus, occlusion of arterial vasculature nourishing the cancer has been
used for palliation for many years. Approaches to occlusive therapy have included surgical
ligation of the common hepatic artery, angiographic occlusion of the common hepatic
artery, or sequential occlusion of selected vasculature supplying the hepatic metastases.
Occlusion of the common hepatic artery can result in higher mortality and morbidity and
shorter duration of palliation; thus, selective vascular occlusion is often preferred.
Hepatic artery occlusion seems particularly effective in palliating
metastases from neuroendocrine tumors because of the tumors increased vascularity. The
methods of achieving hepatic artery occlusion are important. The more central occlusion
the more numerous are the collateral vessels, the more peripheral the occlusion (closer to
the tumor), the less opportunity exists for collateral vessels to form. Because regrowth
of these tumors is often slow, lasting palliative effects are anticipated.
Among the embolic agents most commonly used to accomplish hepatic
artery embolization are absorbable gelatin sponge segments and power (i.e., Gelfoam)
(40-60 µm in diameter) and nonabsorbable polyvinyl alcohol-foam granules (i.e., Ivalon)
(150-250 µm in diameter. Recently, degradable starch microspheres (40 µm) have been used
as embolic agents in several clinical trials, including those with population of patients
with primary or metastatic liver carcinoma. Degradable starch microspheres (40 µm) are
nontoxic and readily degradable and provide temporary vascular occlusion. Degradable
starch microspheres have been used with and without intraarterial chemotherapy, with
reported response rates ranging from 40% to 60% and with a median response duration of
approximately 6 months. Commonly reported complications in all embolization studies have
included fever, abdominal pain, nausea, vomiting, ileus, and transient elevations of liver
enzyme function tests.
Patients with islet cell carcinoma are often treated with systemic
chemotherapy before hepatic artery occlusion, and those with carcinoid tumors are often
treated with somatostatin analogue. The treatment has been influenced by the availability
of somatostatin analogue. The rate of objective regression varies greatly, probably
because of varying definition of response and the bulk of the tumor at the start of
therapy. We have traditionally used embolization or chemoembolization in patients with
moderate to severe symptoms or those with bulky (more than 50% involvement of the liver)
liver metastases with the potential of liver compromise within 4-6 months. Although the
use of chemotherapy drugs with embolization is frequent and sometimes unquestioned, it
remains to be established whether they are advantageous. This issue is not discussed in
the literature. Further research should focus on methods to improve drug-retention time
and new drugs.
