What is carcinoid syndrome?

Carcinoid syndrome affects approximately 20% of people with gastrointestinal NETs.

People with carcinoid syndrome may experience symptoms unexpectedly over time since the hormones may be produced at any time.

This can have a major impact on quality of life.

The main symptoms of carcinoid syndrome include diarrhoea, flushing of the skin (particularly the face), and stomach cramping. Other symptoms may include heart problems such as palpitations, and wheezing.

Symptoms of carcinoid syndrome may be triggered by emotional stress and anxiety, drinking alcohol and caffeinated drinks, and by certain food types.

Untreated carcinoid syndrome can result in vitamin deficiencies and regular bouts of diarrhoea, which can cause dehydration.

Carcinoid syndrome symptoms may be avoided or alleviated, however, by:

• Avoiding stressful situations or practicing relaxation techniques
• Reducing the consumption of alcoholic and caffeinated beverages
• Reducing or avoiding foods that you find trigger symptoms.
• Exercise

Visit the practical tips and tools section for information on managing dietary triggers of diarrhoea and tips to reduce skin flushing.

A more serious, but rare, complication of untreated carcinoid syndrome is carcinoid crisis. This is the immediate onset of debilitating and potentially life-threatening manifestations of the same symptoms that are associated with carcinoid syndrome in a severe form. It usually occurs in those who already have carcinoid syndrome but can occur without having a history.

Carcinoid crisis may be triggered by being given an anaesthetic, having a biopsy taken or undergoing surgery. It is important, therefore, that you let doctors know that you have NETs before undergoing any of these so that precautionary measures can be taken. This may involve having an injection or intravenous infusion of a short-acting somatostatin analogue.

If you have been diagnosed with carcinoid syndrome, you may need medical treatment for specific symptoms you may be experiencing.

These may include a somatostatin analogue, a tryptophan hydroxylase inhibitor, embolisation, PRRT, surgery, interferon therapy, or other medications to help with diarrhoea and skin flushing.

You may also be given medications to help manage wheezing, stomach pain, and any heart problems, such as heart palpitations and high blood pressure.

Always consult your doctor about which medications and surgical options they recommend for your particular symptoms. Their recommendations will be based on your specific NETs diagnosis and overall health.

Somatostatin analogues

Carcinoid syndrome can be treated using hormone therapy with a somatostatin analogue to lessen diarrhoea and skin flushing. Somatostatin analogues can also control the growth of NETs.

Somatostatin analogue injections can reduce the amount of hormones released from NET cells and thus improve symptoms of carcinoid syndrome. Sometimes your doctor will need to adjust the dose or timing of injections to help optimise the control of NETs and any carcinoid symptoms.

Tryptophan hydroxylase inhibitors

Tryptophan hydroxylase (TPH) is a rate-limiting enzyme involved in the synthesis of serotonin, a known hormone which is overproduced in patients with carcinoid syndrome.

An excess of serotonin can cause carcinoid syndrome. One key symptom of carcinoid syndrome is diarrhoea which can be lessened by taking a medication that reduces the activity of TPH (a ‘TPH inhibitor’).

Liver-directed therapies

Liver metastases are the main source of hormones released into the bloodstream in some patients with NETs. Thus treatments that are directed at the liver may help to reduce symptoms of carcinoid syndrome if other methods have not worked.

Liver-directed therapies includes embolisation, which can destroy some of the NET cells in the liver. Such treatment has to be carefully considered and may not be suitable for everyone with NETs.

Radionuclide therapy

Peptide receptor radionuclide therapy (PRRT) has been shown to reduce tumour growth in people with NETs. PRRT may also reduce hormones from being released from NET cells and thus help to reduce the symptoms of carcinoid syndrome.

Debulking surgery

In some cases, surgery to remove some, if not all, liver metastases due to NETs can reduce the ‘bulk’ of NET cells releasing hormones if other treatments have not worked (sometimes called ‘debulking’). This type of surgery reduces the volume of NET cells which in turn should help to reduce the production of hormones that cause the symptoms of carcinoid syndrome.

Interferon-alpha therapy

Treatment with interferon-alpha is sometimes called biologic therapy or immunotherapy and is used to treat some people with NETs. Interferon is a naturally occurring substance that is produced by the body’s immune system during an illness such as a viral infection (e.g. influenza).

Interferon-alpha is given as an injection and it is usually given in combination with somatostatin analogues to try to help the symptoms of carcinoid syndrome, but it can be used on its own.

Interferon may not be a suitable therapy for everyone with NETs.

Liver metastases are the main source of hormones released into the bloodstream in some patients with NETs. Thus treatments that are directed at the liver may help to reduce symptoms of carcinoid syndrome if other methods have not worked.