Surgical resection of non-metastatic carcinoid tumours is usually curative, whilst the management of metastatic disease is focussed on a combination of pharmacological control of the carcinoid syndrome. The latter includes agents that block the synthesis, release and peripheral blockade of circulating tumour products. The list of drugs used in the treatment of carcinoid symptoms include inhibitors of 5HT synthesis such as parachlorophenylalanine, peripheral 5HT antagonists such as cyproheptadine, antihistamines and inhibitors of 5HT release such as somatostatin and its long-acting analogues. The most frequently used somatostatin analogue is octreotide, and this leads to a relief of symptoms in 80% of patients for a median duration of 10 months. Interferon has been used to treat patients with metastatic carcinoid tumours that have become refractory to somatostatin analogues. Symptom relief will occur in 50–70% patients, but fewer than 5% of patients achieve any significant tumour regression. Treatment with interferon is associated with significant side effects, which may include flu-like symptoms; for this reason, it is not generally given.

When metastatic disease in the liver is extensive, hepatic artery embolization, chemoembolization or radioembolization may be considered. This involves selective cannulation of the artery with injection of embolic material. Amongst the substances injected are radiolabelled analogues of somatostatin such as ⁹⁰yttrium DOTA-octreotide and ⁹⁰yttrium-embedded microspheres (see Figure 3.12). This will lead to sustained symptom relief in the majority of patients. There may be significant side effects from embolization, and so this procedure is not entered into without due consideration of the benefits. In some clinical series, mortality rates are 3–5%.

A “landmark” trial comparing treatment with octreotide with everolimus and octreotide was published in 2011. Everolimus is an orally active inhibitor of the mammalian target of rapamycin, an “mTOR inhibitor”. The progression-free survival of the patients treated with combination therapy was 16 months and for those treated with single-agent octreotide was 11 months. As a result of this excellent study of 429 patients, the combination of octretoide and everolimus is now the “standard of care” for patients with metastatic carcinoid syndrome.

The prognosis for patients with metastatic carcinoid tumour is relatively good in comparison to that for most metastatic tumours. Patients with metastatic carcinoid tumour commonly survive a considerable time and the expectation, even in the presence of liver disease, is that approximately 36% of patients will survive 5 years and 20% for 10 years. In the absence of metastases and following resection of the primary, the outlook is excellent. Carcinoid tumours of different primary sites are thought to have different outlooks, but this is very much debated.

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