Lay Sumamry: Interferon is an accepted treatment for carcinoid.
Systemic treatment for NETs includes therapy with somatostatin analogs, interferon-alfa and cytotoxic agents. In addition, other agents can be useful, including loperamide for diarrhea or H1 or H2 blockers for histamine-secreting tumours. Interferon-alfa may be considered in selected cases to control clinical symptoms of hormone hyper-secretion. Symptomatic and biochemical responses are reported in 50% of patients with tumour reduction in 10-15%. There has been biochemical response in 40–60% of patients, symptomatic improvement in 40–70% of patients, and significant tumour shrinkage in a median of 10–15% of patients. In combination with somatostatin analogues, the effect may be enhancedSide effects include flu-like symptoms and autoimmune phenomena (e.g. thyroiditis). It appears to be especially effective when combined with symptomatic treatment of diarrhea.
In one prospective trial of 68 patients with liver metastases who were randomized to octreotide (100 micrograms twice daily, increased to 200 micrograms three times daily for persistent carcinoid symptoms) with or without IFNa, both treatments were equally effective at reducing urinary 5-HIAA levels. Patients receiving combined therapy had a significantly reduced risk of tumor progression when compared to patients receiving octreotide alone, suggesting that the addition of IFN had a significant antitumor effect. Other studies had less impressive results and soem controversy remains. However, interferon is a category 2B recommendation by NCCN (CARC-5)
Arnold R, Rinke A, Klose KJ, Müller HH, Wied M, Zamzow K, Schmidt C, Schade-Brittinger C, Barth P, Moll R, Koller M, Unterhalt M, Hiddemann W, Schmidt-Lauber M, Pavel M, Arnold CN Octreotide versus octreotide plus interferon-alpha in endocrine gastroenteropancreatic tumors: a randomized trial. Clin Gastroenterol Hepatol. 2005;3(8):761.
Kölby L, Persson G, Franzén S, Ahrén BRandomized clinical trial of the effect of interferon alpha on survival in patients with disseminated midgut carcinoid tumours. Br J Surg. 2003;90(6):687.
J K Ramage et al,Guidelines for the management of gastroenteropancreatic neuroendocrine (including carcinoid) tumours Gut 2005;54:iv1-iv16