Neuroendocrine Tumors of the Pancreas
A neuroendocrine tumor of the pancreas develops in the islet cells, which are responsible for the production of hormones. Endocrine cancers occur much less frequently than adenocarcinomas: on average only one out every 100,000 people will develop a neuroendocrine tumor. In the United States, 2,500 people a year are diagnosed with some form of neuroendocrine tumor.
A neuroendocrine tumor is usually less aggressive than an adenocarcinoma, increasing the chances that the growth can be removed before metastasis — spreading to other organs. Depending on the individual growth, the cancer may cause excessive amounts of hormones to flood the body or may entirely shut down hormone production.
Non-Functioning Islet Cell Tumors
Non-functioning islet cell tumors account for sixty percent of all endocrine pancreas cancers. The abnormal cells stop producing hormones. As a result, the often-dramatic symptoms associated with other neuroendocrine tumors are not present, and the affected tissue can grow to large sizes before diagnosis is made. However, non-functioning islet cell cancers are less aggressive than adenocarcinomas and the chance is much higher that metastasis will not have occurred at the time of diagnosis. Symptoms are usually vague if they are even present, and include abdominal pain and jaundice.
Functioning Islet Cell Tumors
Functioning islet cell tumors differ from non-functioning growths in that they produce excessive amounts of hormones. This can lead to a wide range of symptoms, including stomach ulcers, diabetes, diarrhea, abnormal blood sugar levels, and skin rashes. Of the different varieties of functioning neuroendocrine tumors, insulinoma and gastrinoma are the most common.
Insulinoma and Blood Sugar Levels
Insulinoma affects insulin producing cells, resulting in the production of large amounts of insulin, which causes low blood sugar levels (hypoglycemia). Hypoglycemia can cause symptoms such as fatigue, hunger, weakness, tremors and confusion.
Women develop insulinoma more often than men. In ninety percent of all cases the growths are benign and usually quite small in size. If the insulinoma is removed surgically, ninety percent of patients require no further treatment.
Gastrinoma and Stomach Ulcers
Sixty percent of gastrinomas (also known as Zollinger-Ellison Syndrome) are malignant and although slow growing, the vast majority have metastasized at the time of diagnosis. Gastrinomas affect islet cells that produce the digestive hormone gastrin. Recurring stomach ulcers, possibly accompanied by an almost constant need for ulcer medication, suggest the possibility of gastrinoma. Ulcer symptoms are treated with omeprazole (Prilosec, Losec).
Long-term survival rates after surgical removal of a gastrinoma are estimated to be approximately 34 percent.
Glucagonoma, Skin Rashes and Diabetes
Glucagonoma affects the production of glucagon, which helps control blood sugar levels. Red, flaky skin rashes that resemble eczema are the most noticeable symptoms of glucagonoma. Two-thirds of patients with glucagonoma may develop diabetes. Weight loss and a lack of appetite may also occur due to high levels of glucagon.
VIPoma (Vasoactive Intestinal Peptide-Producing Tumors)
VIPomas are also known as watery diarrhea hypokalemia hypochlorhydia syndrome. VIPomas affect the intestine’s ability to absorb water resulting in watery diarrhea, often accompanied by potassium deficiencies. Diarrhea can become so severe that hospitalization and intravenous rehydration are required.
Cancer of the endocrine pancreas includes a highly treatable and often curable collection of tumors. They are uncommon cancers with 200 to 1,000 new cases per year and occur in only 1.5% of detailed autopsy series. Islet tumors may either be functional (produce one or more hormones) or nonfunctional. The majority of functioning tumors that produce insulin are benign; however, 90% of nonfunctioning tumors are malignant. Many islet cell cancers are nonfunctional and produce symptoms from tumor bulk or metastatic dissemination. Because of the presence of several cell types in the pancreatic islet cells (alpha, beta, delta, A, B, C, D, E), the term islet cell tumors refers to at least five distinct cancers, which when functional, produce unique metabolic and clinical characteristics. Since the clinical manifestations in functional tumors may result from the metabolic effects of polypeptide(s) secreted by the cancer cells rather than from tumor bulk or metastatic disease, each tumor type must be considered separately, both diagnostically and therapeutically.[1-3] Functional tumors may be too small in size to be detected by conventional imaging techniques.
The frequent long delays between initial symptoms and diagnosis and the varied effects of the polypeptides secreted often necessitate involvement of multiple surgical and medical subspecialties. Surgery is the only curative modality.[4,5] Even in those cases not resectable for cure, effective palliation may be achieved because of the slow-growing nature of the majority of these tumors and the potential use of antihormonal pharmacologic therapy (for example, cimetidine in the ulcer-producing Zollinger-Ellison syndrome). Combination chemotherapy may provide effective palliation as well as increased survival in selected patients. In patients with indolent, slow-growing metastatic islet cell tumors, the best therapy may be careful observation and no treatment until palliation is required. Patients with multiple endocrine neoplasia syndrome type 1, an autosomal dominant condition in which 85% have pancreatic islet cell tumors, 90% have hyperparathyroidism, and 65% have pituitary tumors, are less likely to be cured by pancreatic resection than are patients with sporadic islet cell tumors. With the exception of pain relief from bone metastases, radiation therapy has a limited role in this disease.
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References
1. Kent RB 3rd, van Heerden JA, Weiland LH: Nonfunctioning islet cell tumors. Ann Surg 193 (2): 185-90, 1981.
2. Modlin IM, Lewis JJ, Ahlman H, et al.: Management of unresectable malignant endocrine tumors of the pancreas. Surg Gynecol Obstet 176 (5): 507-18, 1993.
Somatostatinoma
Somatostatinoma is one of the rarest of the endocrine cancers. Somatostatin regulates the production of all other endocrine pancreas hormones. If somatostatin levels rise due to tumor activity, a wide range of hormonal symptoms can occur, including diabetic symptoms, gallstones, diarrhea and constipation.
Treatment Options
If metastasis of the neuroendocrine tumor has not occurred, surgical removal is the preferred form of treatment. Surgical removal of neuroendocrine tumors has a much higher success rate than with adenocarcinomas. Even if metastasis to local lymph nodes has occurred, surgery may still be an option for a patient.
Resources
Endocrineweb.com. (nd). Endocrine tumors of the pancreas. Retrieved March 21, 2003, from http://www.endocrineweb.com/pancreas.html.
Eriksson, B. (2000). Neuroendocrine pancreatic tumors: Clinical presentation, diagnosis and medical treatment. CARPA bulletine 1. Retrieved March 21, 2003, from www-pp.hogia.net/carpa/neuroendo en.html.