Carcinoid Syndrome

Treatment of the carcinoid syndrome is more complicated because it is often associated with hepatic metastases. Carcinoid syndrome occurs with 5% of all neuroendocrine tumors but occurs more often in patients with small bowel carcinoids.59 Many different approaches, such as liver resection, tumor debulking, radiofrequency ablation, chemoem-bolization, and liver transplantation, as well as treatment with somatostatin analogs and interferon-a make it difficult to choose the optimal therapy. Therapy should be guided by whether curative or palliative therapy is possible and whether the endocrine symptoms or the tumor burden is the problem.

Despite the development of potent drugs for controlling carcinoid syndrome, surgery is still the treatment of choice for possible cure. When liver metastases are resectable, hepatectomy should be performed and the primary intestinal tumor removed.45,60,61 Even when hepatic metastases are diffuse, operative intervention is critical in one or multiple stages.61 Tumor debulking can control carcinoid syndrome and reduce urinary 5-HIAA levels. The occurrence and severity of the syndrome are clearly related to tumor bulk. However, the tumor mass must be reduced to 10% to 20% to control the symptoms when cytoreductive hepatic surgery is performed.62 With the advent of somatostatin analogs, the role of surgical debulking may be restricted to low-risk patients with one dominant tumor mass that did not respond to somatostatin treatment. Liver transplantation for diffuse hepatic metastases may be considered in selected patients when extrahepatic metastases have been excluded.26,63 Methods for in situ destruction of liver tumors (radiofrequency, cryotherapy, or laser ablation) are new alternative regional treatment options. The long-term survival benefit of these interventions is not yet known.60,64 Neither systemic chemotherapy nor hepatic dearterialization has been effective in controlling tumor growth and symptoms.1,65 Chemoembolization with superselective occlusion, however, controls the tumor burden and symptoms in up to 80% of the patients for an average duration of 11 months.66,67

Somatostatin has become the most important drug in the medical treatment of neuroendocrine tumors. It alleviates carcinoid syndrome symptoms in about 80% of patients at a dosage of 200 to 600 (Xg/day. The duration of remission, however, is short with a median of 8 to 12 months. Although biochemical markers transiently decrease in about 70% of

No Symptoms

Incidental guiding at operation

Clinical Syndrome

Biochemical evaluation Diagnostic localization

Oncologic resection (exceptions: duodenum, appendix, rectum)

Hepatic metastases.

+SMS

Hepatic resection Chemoembolization Octreotide (SMS)

FIGURE 86-5. Therapy for carcinoid tumors. IFN = interferon; SMS = somatostatin.

patients, tumor size reduction resulting from the antiproliferative effect of somatostatin analogs occurs in fewer than 10% of patients. Stabilization of tumor growth, however, occurs in about 50% of patients with a median response of about 18 months.68,69 Somatostatin should be administered before tumor manipulation, including all operative procedures and catheter embolization. Somatostatin reduces the risk of severe flushing resulting from massive release of hormones and kinins.70 Interferon-a inhibits tumor proliferation with short-term relief from the carcinoid syndrome. Interferon-a alone or in combination with somatostatin analogs and interferon in combination with fluorouracil may result in a biochemical response in up to 50% of patients, but evidence of tumor regression is reported in only 10% to 20% of patients.1,71 Thus, resection of hepatic metastases can be performed with curative intention or for symptomatic relief. Another attractive option is cytoreduction by multimodal therapy (Fig. 86-5). Hepatic radioembolization and somatostatin receptor-targeted radiotherapy are new approaches to localized radiotherapy and are under clinical evaluation.26

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