Carcinoid syndrome is a pattern of symptoms that occurs in people who have carcinoid tumours. The symptoms are caused by hormones and chemicals produced by the carcinoid tumour and, in many cases, these symptoms are actually worse than the effects of the growth of the tumour itself.
Carcinoid tumours were first identified in Europe in the mid-1800s as a specific, distinct type of growth. The name carcinoid was first used in 1907 to classify them as a type of tumour that fit midway between malignant (cancerous) tumours and ones that were benign (non-malignant).
Carcinoid tumours can be widely distributed throughout the body, but are usually found in the digestive system (50% of cases) or lung (30% of cases). In children, carcinoid tumours are usually found in the appendix. Once the appendix is removed, the cancer is usually cured.
Carcinoid tumours produce too much of certain chemicals and hormones and this can cause reactions in the body. One common chemical produced by carcinoid tumours is a hormone called serotonin. This hormone makes the blood vessels dilate (widen) and causes increased blood clotting, intestinal secretions, and motility (causing diarrhea).
Carcinoid tumours are rare, with 1 to 2 cases in every 100,000 people. It makes up less than 1% of all cancers.
Carcinoid tumours have been called "cancers in slow motion" because they tend to grow so slowly that people who have them usually live for many years, and sometimes have a normal lifespan. Unfortunately, some carcinoid tumours produce large amounts of hormones and other potent chemicals. This can cause "carcinoid crisis" or carcinoid syndrome, which may occur infrequently at first but may gradually happen more often.
Carcinoid syndrome often occurs without an obvious cause, but may be brought on by alcohol use or physical or emotional stress.
Serotonin is the most commonly produced chemical, but not all carcinoid tumours produce the same large variety of chemicals and hormones. It’s not known which of the substances cause each of the symptoms of carcinoid syndrome.
The most pronounced and bothersome symptoms of carcinoid syndrome include episodic bright red flushing of the head, neck, and upper chest, abdominal pain, and diarrhea (which may be severe). Sometimes, people will also notice wheezing. The flushing often happens after emotional stress, eating certain foods, or drinking alcohol or a hot beverage.
Other less common symptoms include a rapid pulse, swelling in the face and around the eyes, low blood pressure, and weight loss due to diarrhea or the inability of the intestines to absorb nutrients. A few people may experience impotence and a decreased sex drive. A specific type of heart valve damage can occur in some cases, as well as other related heart problems.
The symptoms of carcinoid syndrome are usually controllable with medication. Most complications arise as a result of the carcinoid tumour, and the disease will progress differently for people with carcinoid syndrome than in those without it. However, the outlook is much better now that there are available treatments (e.g., octreotide*).
Many years ago, the harmful effects of the potent hormones released by the tumours were fatal, and death due to the tumour’s growth and spread occurred in 25% of cases. Today, with effective combinations of treatments using medication, various types of surgery, chemotherapy, and other methods, the average survival time has improved.
Most individuals with non-functioning carcinoid tumours (ones that aren’t secreting) go for many years with no symptoms. It’s usually only when abdominal pain and a change in bowel habits occur that they see their doctor. Once these symptoms are investigated, the doctor can determine the cause.
Carcinoid syndrome can be easily diagnosed when all of its features, or even one or two of its main symptoms, are present. However, because the syndrome is rare, even when there are many symptoms, it may be overlooked.
If carcinoid syndrome is suspected, the diagnosis usually can be confirmed quickly and painlessly by doing a urine test for 5-HIAA (5-hydroxyindole acetic acid – the waste product of serotonin). By measuring the amount of 5-HIAA in the urine over a 24-hour period, your doctor can tell how much serotonin is produced during that time. In carcinoid syndrome, the amount of 5-HIAA is almost always above normal.
This test is very good at identifying active disease; however, it may miss non-secreting carcinoid tumours or it may give false-positive results since some foods and medications can also cause high 5-HIAA levels in the urine.
Preparation for the 5-HIAA test requires avoiding certain foods and medications for a day or two before the test, as they may cause inaccurate test results. These include:
Sometimes the 5-HIAA in the urine won’t be higher than normal, but other carcinoid markers in the blood, such as chromogranin A and serotonin, will be. The tryptophan level in the blood is usually lower than normal.
Standard X-ray and imaging tests are then used to find the location of the tumour and identify how far it has spread. These tests may include a routine chest X-ray, CT or MRI scan, barium enema, and upper GI (gastrointestinal) and small bowel X-ray studies. Occasionally, it is also helpful to have an upper and lower GI tract endoscopy, which is a procedure that uses a flexible fibre optic tube to look inside the GI. However, these tests do not detect all carcinoid cases.
Another useful though expensive method of finding about 85% of carcinoid tumours is an OctreoScan. This involves injecting a tiny dose of a radioactive isotope that’s specifically attracted to, and concentrated in, carcinoid tumour tissue. Carcinoid tumours then light up when a radiation scan is taken over the entire body, thus pinpointing the tumour location. The harmless radioactive isotope is excreted by the body in a few days.
An OctreoScan can be very helpful in confirming the diagnosis and locating the tumour in the rare cases of carcinoid syndrome, where all the symptoms and chemical findings are known but tests to locate the tumour turn up negative.
Surgical removal of carcinoid tumours can result in a complete and permanent cure of carcinoid syndrome. If it’s not possible to completely cut out all the tumour tissue, removing large portions of the tumour (debulking) can reduce the symptoms. Because most carcinoid tumours are very slow growing, debulking may relieve symptoms for a long time.
Injection of octreotide may reduce the symptoms of carcinoid syndrome and even inhibit or reverse tumour growth.
Techniques called cryoablation or radiofrequency ablation use probes that freezes or use radio waves to destroy carcinoid tumour metastases (parts of the tumour that have spread) in the liver that can’t be removed surgically.
Another way of debulking is to inject the liver artery that supplies blood to the tumour with a combination of embolic (blocking) material and chemotherapy medications. This shuts off the blood flow with its oxygen supply to the tumour and loads the tumour with tumour-destroying and growth-inhibiting chemotherapy. This way the chemotherapy is concentrated in the tumour, where it can have a much stronger effect.
Radiation treatment may also be used to treat carcinoid tumours. At some treatment centres, radioactive isotopes bound to specific chemicals or medications that readily collect in carcinoid tumours are injected to help control the disease.
It’s important to have a diet high in protein if you have carcinoid syndrome. Your diet should also be supplemented with certain vitamins, such as niacin, as well as minerals (potassium, magnesium, calcium, iron, and salt) when these are low due to diarrhea. Various medications may also be prescribed to control diarrhea and flushing. Antihistamines and other medications are sometimes used to prevent carcinoid syndrome attacks.
People with carcinoid tumours should avoid alcohol as well as physical and emotional stress, since these can cause carcinoid crisis attacks. For the same reason, people should avoid adrenaline-like medications, including nasal decongestants and some asthma inhalers. Although some symptoms of carcinoid syndrome can be prevented with medication, the best way to prevent carcinoid syndrome is to treat the carcinoid tumour.
*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.
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