Carcinoid tumors: What should increase our suspicion?
ABSTRACTCarcinoid tumors are neuroendocrine neoplasms, primarily of the gastrointestinal tract. Their incidence has been increasing over the last 2 to 3 decades. Patients often present with vague, nonspecific symptoms. Thus, primary care physicians should keep this diagnosis in mind and start appropriate diagnostic testing if they suspect it on a clinical basis. Patients with carcinoid tumors are also at increased risk of developing other malignancies, so close follow-up by their primary care physician is necessary.
KEY POINTS
- Bioactive compounds secreted by carcinoid tumors cause carcinoid syndrome—ie, bronchospasm, diarrhea, cutaneous flushing, and right-sided valvular heart lesions.
- Endocardial fibrotic plaques can occur in patients with carcinoid tumors. The right side of the heart is affected more often than the left, as the left side is protected by inactivation of the bioactive compounds in the lungs. Tricuspid valve regurgitation is the most common finding.
- Since carcinoid tumors have high concentrations of somatostatin receptors, octreotide scanning offers a distinct advantage in imaging them: use of radiolabeled octreotide, a somatostatin analogue, enables imaging of primary tumors and metastases.
LONG-TERM PROGNOSIS IS GENERALLY GOOD
The prognosis for patients with carcinoid tumors depends on the location and extent of disease. Tumors of the appendix and rectum have the best prognosis, with 5-year survival rates approaching 100% for localized carcinoid tumors of the appendix.3,21 In contrast, tumors of the small bowel, especially the ileum, are more aggressive and have the worst prognosis (a 5-year survival rate of about 60% to 65%).21
COMPLICATIONS
Other primary malignancies
Carcinoid tumors are often associated with the development of other tumors, not always in the gastrointestinal tract. As many as 52% of patients with small-bowel carcinoid tumors develop another primary tumor.22 This effect is thought to be related to the tumorigenic properties of the bioactive compounds secreted by carcinoid tumors. The other primary malignancy can be synchronous (diagnosed at the same time) or metachronous (diagnosed 1 to 7 years after the carcinoid) and generally arises from the gastrointestinal, genitourinary, or respiratory tract. Adenocarcinoma of the colon is reported as the most common second primary malignancy in patients with carcinoid tumors.22
The best strategy for surveillance in these patients is still unclear. Screening for tumors of the colon, small bowel, lung, cervix, and ovaries at the time of carcinoid tumor diagnosis followed by surveillance for these malignancies has been suggested as a possible approach; however, this comes at the cost of increased patient anxiety, cost, and morbidity from testing. 3
Carcinoid crisis
Carcinoid crisis is a life-threatening emergency caused by release of large amounts of vasoactive compounds from the carcinoid tumor, either spontaneously or provoked by tumor manipulation, surgery, chemotherapy, or hepatic artery embolization.2,5 The syndrome manifests as cardiovascular collapse (severe hypotension or hypertension), tachycardia, and altered mental status.
Treatment differs from those for other causes of shock in that catecholamines and calcium should not be used since they trigger the release of larger amounts of bioactive chemicals from the tumor. In addition, the shock in this situation is refractory to fluid. The mainstay of treatment is the infusion of octreotide and plasma. This crisis can be prevented by giving octreotide before manipulating the tumor.1,2,5
