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Carcinoid syndrome refers to the array of symptoms that occur secondary to carcinoid tumors. Carcinoid tumors are discrete, yellow, well-circumscribed tumors that can occur anywhere along the gastrointestinal tract (GI). They most commonly affect the appendix, ileum, and rectum. These tumors are unique in that they are endocrine in nature. They secrete hormones into the blood stream, which then travel to end organs and act upon them via appropriate receptors. Although quite rare, 15 cases/1,000,000 population, carcinoid tumors account for 75% of GI endocrine tumors.
Pathophysiology
Carcinoid tumors secrete vasoactive substances such as serotonin, histamine, catecholamines, and prostaglandins. These hormones acts upon many tissues of the body including the central nervous system, blood vessels of the intestinal tract, and platelets, ultimately altering blood flow. Prior to metastasis, the liver is capable of metabolizing most of the hormones elaborated by such tumors, rendering patients asymptomatic. Only about 5% of patients with carcinoid tumors ever develop symptoms of the carcinoid syndrome which includes, flushing, diarrhea, hypotension, edema, asthma-like bronchoconstriction attacks, and valvular heart disease. The onset of these symptoms suggests that the tumor has metastasized to the liver, allowing serotonin and its various by-products to reach systemic circulation.
Diagnosis
With a certain degree of clinical suspicion, diagnosis is made primarily by measuring plasma levels of the secreted glycoprotein Chromogranin A, supported by measuring the 24 hour urine levels of 5-HIAA (5-hydroxyindoleacetic acid), a breakdown product of serotonin. Patients with carcinoid syndrome usually excrete >25 mg of 5-HIAA per day. For localization of both primary lesions and metastasis, the initial imaging method is Octreoscan, where Indium labelled somatostatin analogues (octreotide) are used in scintigraphy for detecting tumors expressing somatostatin receptors. Median detection rates with octreoscan are about 89%, in contrast to other imaging techniques such as CT scans and MRI with detection rates of about 80%. PET scans, which evaluate for increased metabolism of glucose, may also aid in localizing the carcinoid lesion or evaluating for metastases.
Treatment
For symptomatic relief of carcinoid sydrome:
- Octreotide (somatostatin analogue- neutralizes serotonin and decreases urinary 5-HIAA)
- Methysergide maleate (antiserotonin agent but not used because of serious side effect of retroperitoneal fibrosis)
- Cyproheptadine (antihistamine)
- Surgical resection of tumor and chemotherapy (5-FU and doxorubicin)
Prognosis
Prognosis varies from individual to individual. It ranges from a 95% 5 year survival for localized disease to a 20% 5 year survival for those with liver metastases. However, median survival for patients with carcinoid sydrome is 2.5 years from the first episode of flushing, without treatment with Sandostatin. The average survival time from the start of Sandostatin treatment has increased to about 12 years.
Synonyms
Thorson-Bioerck syndrome, argentaffinoma syndrome, Cassidy-Scholte sydrome, flush syndrome
References
- "Endocrine Tumors of the GI Tract and Pancreas." Harrison's Manual of Medicine. Eugene Braunwald. 15th edition. New York: McGraw-Hill, 2002. 298-299.
- "Malignant Carcinoid Syndrome." Current Medical Diagnosis & Treatment. Lawrence M. Tierney, Jr. 43rd edition. New York: Lange Medical Books/McGraw-Hill, 2004. 1625.
- "Carcinoid Syndrome." Griffith's 5 Minute Clinical Consult. Mark Dambro. Mobile Version 6.0.139. Lippincott, Williams and Wilkins, 2003.
- "Current Status of Gastrointestinal Carcinoids." Gastroenterology. Irvin M. Modlin et al. 2005;128;1717-1751.
See also
External links
- Merck
- http://www.carcinoid.org
- http://www.netumoradvisor.org
"Carcinoid syndrome"