Carcinoid Syndrome

Definition

Definition of Carcinoid Syndrome
Carcinoid syndrome refers to the array of symptoms that occur secondary to carcinoid tumors. The syndrome includes flushing and diarrhea, and, less frequently, heart failure and bronchoconstriction. It is caused by endogenous secretion of mainly serotonin and kallikrein.

Symptoms

Symptoms of Carcinoid Syndrome
Most carcinoid tumors have no symptoms. When symptoms do occur, they may include:

1. Abdominal pain that comes and goes
2. Bright red flushing of the face, neck, or upper chest
3. Diarrhea
4. Heart palpitations
5. Low blood pressure
6. Wheezing

Causes

Causes of Carcinoid Syndrome
Carcinoid syndrome is the pattern of symptoms sometimes seen in people with carcinoid tumors. These tumors are rare, and often slow growing. About 70% of carcinoid tumors are found in the gastrointestinal tract.

Carcinoid syndrome occurs in about 1 in 10 people with carcinoid tumors, usually after the tumor has spread to the liver or lung.

Diagnosis

Diagnosis of Carcinoid Syndrome
With a certain degree of clinical suspicion, the most useful initial test is the 24 hour urine levels of 5-HIAA (5-hydroxyindoleacetic acid), the end product of serotonin metabolism. Patients with carcinoid syndrome usually excrete more than 25 mg of 5-HIAA per day. For localization of both primary lesions and metastasis, the initial imaging method is Octreoscan, where indium-111 labelled somatostatin analogues (octreotide) are used in scintigraphy for detecting tumors expressing somatostatin receptors. Median detection rates with octreoscan are about 89%, in contrast to other imaging techniques such as CT scan and MRI with detection rates of about 80%. Gallium-68 labelled somatostatin analogues such as 68Ga-DOTA-Octreotate (DOTATATE), performed on a PET/CT scanner is superior to conventional Octreoscan. Usually on CT scan, one will note a spider-like/crab like change in the mesentery due to the fibrosis from the release of serotonin. 18F-FDG PET/CT, which evaluate for increased metabolism of glucose, may also aid in localizing the carcinoid lesion or evaluating for metastases. Chromogranin A and platelets serotonin are increased.

Treatment

Treatment of Carcinoid Syndrome
Surgery to remove the tumor is usually the first treatment. It can permanently cure the condition if the tumor is completely removed. If the tumor has spread to the liver, treatment involves destroying the local blood supply of the tumor or giving chemotherapy directly into the liver.  When the entire tumor cannot be removed, removing large portions of the tumor ("debulking") can help relieve the symptoms.

Octreotide injections are sometimes given to people with advanced carcinoid tumors that cannot be removed with surgery. Interferon is often given with octreotide to help stop tumor growth. Patients whose carcinoid tumor secretes histamine will benefit from treatment with antihistamine drugs.

People with carcinoid syndrome should avoid alcohol, large meals, and foods high in tyramine (aged cheeses, avocado, many processed foods), because they may trigger symptoms.

Some common medicines, like selective serotonin reuptake inhibitors (SSRIs), such as paroxetine (Paxil) and fluoxetine (Prozac), may make symptoms worse by increasing levels of serotonin. However, do not stop taking these medicines unless your doctor tells you to do so.

Prognosis

Prognosis of Carcinoid Syndrome
The outlook in patients with carcinoid syndrome is different from the outlook in patients who have carcinoid tumors without the syndrome.

In people with the syndrome, the tumor has usually spread to the liver, which lowers the survival rate. People with carcinoid syndrome are also more likely to have a separate cancer (second primary tumor) at the same time.

Prevention

Prevention of Carcinoid Syndrome
Treating the tumor reduces the risk of carcinoid syndrome.