Carcinoid syndrome: symptoms, causes and treatment

Cancer Research UK explains that some neuroendocrine tumours (NETs) make large amounts of hormones and proteins. The most common substance they make is serotonin. They sometimes release serotonin and other proteins into the bloodstream, and this can cause a collection of symptoms called carcinoid syndrome.

The syndrome is therefore not a cancer in itself but a set of symptoms caused by hormone release from a NET. It is most common in people with a small bowel NET that has spread to the liver, and can also occur with lung and pancreatic NETs, though less commonly.

Cancer Research UK also says it is much more common for NETs to produce abnormal levels of hormones than neuroendocrine carcinomas (NECs), which almost never have symptoms linked to making an abnormal amount of hormones.

Cancer Research UK lists two main symptoms. The first is flushing of the skin: the skin of the face, neck and chest might look red and may feel warm and itchy. About 85% of people with carcinoid syndrome have this. Flushing is often unexpected and unpredictable, and some people notice triggers such as certain foods, coffee or alcohol, stress or exercise.

The second is diarrhoea, which means changes in the consistency, frequency or volume of your poo. It can be severe: Cancer Research UK says some people with carcinoid syndrome have diarrhoea more than 30 times a day. About 80% of people with carcinoid syndrome have diarrhoea.

• Tummy (abdominal) pain.

• Red spidery marks on the skin caused by small broken blood vessels (telangiectasia).

• A whistling sound when breathing (wheezing).

• Fast heartbeat and palpitations.

• A build-up of fluid in the legs and ankles.

Cancer Research UK says you usually have several tests, which also help your doctor plan treatment.

Cancer Research UK says the main aim of treatment is to reduce symptoms by reducing the amount of hormones and proteins the NET is making. This will not get rid of the NET but can control symptoms and help you feel better. Treatment also aims to prevent carcinoid heart disease, or stop it causing further damage, and to make sure you get the right nutrition.

The main treatment is a somatostatin analogue such as octreotide or lanreotide, which can lower the hormones that cause carcinoid syndrome and help control symptoms such as diarrhoea and flushing. They might also shrink the tumour.

If that does not work, the doctor might suggest surgery to remove the cancer from the liver or as much as possible of it (debulking surgery), trans-arterial embolisation (TAE) to block the blood supply to a NET in the liver, selective internal radiation therapy (SIRT), peptide receptor radionuclide therapy (PRRT) or a targeted cancer drug called everolimus. Specialist neuroendocrine tumour teams decide which option suits which person.

Cancer Research UK says that you do not need to follow any special diet if you are able to follow a normal, healthy diet, are a healthy weight and do not have side effects causing problems. If you do have diet problems, talk to your dietitian, doctor or specialist nurse.

It lists foods that trigger carcinoid syndrome among the causes of diarrhoea in neuroendocrine cancer, alongside abnormal hormone production, surgery to the bowel or pancreas and treatment side effects. If you have diarrhoea, it advises drinking little and often, aiming for at least 2 or 3 litres a day, and eating small meals and snacks regularly. Although a high-fibre diet is usually healthier, it can make diarrhoea worse, so it suggests foods such as white rice, white pasta, well-cooked eggs and white bread.

Problems absorbing fat can cause pale, offensive-smelling stools that float (steatorrhea). Cancer Research UK says to talk to your doctor or specialist nurse, who can prescribe pancreatic enzyme supplements. It also says your healthcare team will decide whether you need extra support with nutrition and may refer you to a dietitian.

Rarely, people with carcinoid syndrome may develop carcinoid heart disease or carcinoid crisis, and Cancer Research UK says doctors check for these regularly.

Carcinoid heart disease happens when plaque or scar tissue builds up in the heart valves and heart muscle; over time the valves thicken, which can affect how the heart works. It happens in up to 50 out of every 100 people with carcinoid syndrome. Symptoms are usually vague and most people have none until it is severe; they include breathlessness, tiredness, swelling from fluid build-up and weight loss. Treatment includes the same medicines to lower hormone levels, heart medicines, dietary changes such as being careful with fluid and salt, and surgery to replace affected valves.

Carcinoid crisis is a more serious version of carcinoid syndrome. It can happen for no reason, and an anaesthetic or treatment such as surgery or chemotherapy can set it off. Symptoms are severe and may include sudden severe changes in blood pressure that could make you dizzy and pass out, palpitations, difficulty breathing with wheezing, sudden severe redness of the skin, and very severe diarrhoea. It is a medical emergency: contact your doctor and go to your local A&E if you think you have this.

To prevent carcinoid crisis, you might have octreotide as an injection or a continuous drip into a vein, especially before, during and after surgery.

See your GP if you have unexplained, recurring flushing or persistent diarrhoea, particularly alongside tummy pain or wheezing. These symptoms have many causes, most of them far more common than carcinoid syndrome, but they need assessing. If you already have a diagnosed NET, contact your specialist team about new or worsening symptoms.

Go to A&E if you have sudden severe flushing, a severe drop in blood pressure causing dizziness or collapse, difficulty breathing with wheezing or very severe diarrhoea, particularly if you have a known NET or are around the time of surgery or treatment. Cancer Research UK says carcinoid crisis is a medical emergency.

On the NHS, carcinoid syndrome is investigated and managed by specialist neuroendocrine tumour teams, usually through referral from a GP or hospital doctor, with input from oncologists, endocrinologists, gastroenterologists, surgeons, dietitians and specialist nurses. Some people also see a specialist privately for opinions or scans. Because treatment is complex, care is usually coordinated through a specialist multidisciplinary team whichever route you take.