Management of metastatic disease from neuroendocrine cancers
What is the carcinoid syndrome and carcinoid heart disease?
The term carcinoid syndrome refers to a constellation of symptoms mediated by various humoral factors, namely serotonin and the tachykinins, elaborated by carcinoid tumors. In the presence of localized disease, carcinoid neoplasms produce 5-hydroxytryptamine, which is taken up and stored in the platelets while the excesses are inactivated from the liver and lung and transformed into 5-hydroxyindoleacetic acid (5-HIAA). In the presence of liver metastases, however, patients may develop the malignant carcinoid syndrome, which results when vasoactive substances produced by the carcinoid tumor escape hepatic degradation and gain access into the systemic circulation. It is also due to the high level of 5-HT degradation by the liver that it is relatively uncommon for disease localized to the gut to display symptoms of serotonin secretion. Clinical findings of the carcinoid syndrome include skin flushing, excessive diarrhea, right-sided heart disease, and bronchoconstriction.
Nearly 40% of patients exhibiting the carcinoid syndrome will develop carcinoid heart disease (CHD) with fibrotic endocardial plaques and associated heart valve dysfunction that classically involves the tricuspid valve. Advanced changes of tricuspid valvular disease has been shown to be associated with poor long-term survival, and carcinoid valvular disease, rather than tumor dissemination, is the cause of death in approximately one-third of these patients. Serotonin is presumed to be the catalyst for the cardiac fibrotic process. Nearly 95% of patients with present with right-sided heart valve disease, characterized by tricuspid insufficiency and pulmonary stenosis and the subsequent development of pulmonary hypertension. Left-sided cardiac disease may be seen in up to 10% of patients, as is commonly associated with angina and coronary vasospasm.