Carcinoid tumors and carcinoid syndrome

ALSO KNOWN AS: Gastrointestinal tract tumors, adenocarcinoid tumors

RELATED CONDITIONS: Colon cancer, small bowel lymphoma

DEFINITION: A carcinoid tumor arises from hormone-producing cells that line the small intestine, appendix, bronchi, colon, pancreas, ovaries, testes, bile ducts, gallbladder, stomach, and liver. Carcinoid syndrome is a group of symptoms caused by the release of hormones from a carcinoid tumor.

Risk factors: No risk factors for carcinoid syndrome or carcinoid tumors have been identified. However, they are thought to be related to a genetic mutation that is either inherited or spontaneous.

Etiology and the disease process: Carcinoid tumors are slow-growing tumors that develop from enterochromaffin cells. These cells secrete hormones such as serotonin, histamine, prostaglandins, polypeptides, and tachykinins. Some 65 percent of carcinoid tumors occur in the gastrointestinal tract, and 25 percent are found in the lungs. The remaining 10 percent arise from other organs, or the primary site is unknown. Benign carcinoid tumors are small and have a low rate of recurrence. Malignant carcinoid tumors tend to be larger than 2 centimeters (cm) and are more likely to metastasize (spread to other organs). They also can invade adjacent tissue.

The hormones secreted by gastrointestinal carcinoid tumors are broken down in the liver, so patients with these types of tumors do not experience carcinoid syndrome. However, if there are liver metastases, carcinoid syndrome can develop. Carcinoid tumors of the lungs, ovaries, and testes are more likely to cause carcinoid syndrome.

Incidence: Research suggests a rate of from 1.5 to 8 cases per 100,000 people. Carcinoid syndrome is rare.

Symptoms: Large gastrointestinal tumors may cause abdominal pain, abdominal mass, bleeding, nausea and vomiting, obstruction, and diarrhea.

Carcinoid tumors of the lungs cause coughing, chest pain, wheezing, blood-tinged sputum, and pneumonia. Lung carcinoid tumors cause carcinoid syndrome about 20 percent of the time.

The most common symptom of carcinoid syndrome is facial flushing, which can last hours to days. Other common symptoms are diarrhea, abdominal pain, wheezing, valvular heart disease, sweating, rapid heart rate, weight gain, weakness, secondary diabetes, and increased body and facial hair. These symptoms are caused by the high levels of hormones released by the tumor.

Screening and diagnosis: Carcinoid tumors are not routinely screened. Larger carcinoid tumors can be diagnosed by computed tomography (CT) scans or magnetic resonance imaging (MRI). If the CT scan shows abnormal lymph nodes or a liver tumor, a needle biopsy can be performed.

Carcinoid tumors can also be found by somatostatin (a hormone) receptor scintigraphy, a nuclear imaging scan. This scan uses indium 111 octreotide as a radioactive dye. Octreotide has an affinity for hormone-producing cells. This test is quite accurate, but it can miss very small tumors and tumors that do not have somatostatin receptors.

Two other nuclear imaging procedures are used: positron emission tomography (PET) and metaiodobenzylguanidine (MIBG) scans. The PET scan picks up areas of the body with higher-than-normal metabolism. Like octreotide, MIBG is attracted to carcinoid tumors.

The only way to verify that a tumor is a carcinoid tumor is to biopsy it. Biopsy may be done by endoscopy, bronchoscopy, or needle biopsy.

A twenty-four-hour urine test for 5-hydroxyindolacetic acid (5-HIAA) can diagnose carcinoid syndrome. The normal urinary excretion rate of 5-HIAA is 8 milligrams (mg). Persons with carcinoid syndrome can excrete between 100 and 2,000 mg of 5-HIAA.

The staging for carcinoid tumors is based on the primary site.

Treatment and therapy: If a carcinoid tumor is less than 2 centimeters (cm) in size, it can be removed by surgery. If the carcinoid tumor is larger than 2 cm, there are multiple tumors, or there are metastases, a cure is less likely. Surgery may be performed to ease the symptoms of the tumor or the carcinoid syndrome.

Sometimes the goal of surgery is debulking (decreasing the tumor size). This is done to decrease symptoms of carcinoid syndrome or in preparation for chemotherapy or radiation therapy. Debulking can be performed by surgical resection, cryoablation (freezing), radiofrequency ablation (radiation), or hepatic artery embolization (blocking the blood supply to the liver).

Chemotherapy may be used to treat carcinoid tumors. The chemotherapeutic drugs most frequently used are 5-fluorouracil (Adrucil), cyclophosphamide (Cytoxan), streptozocin (Zanosar), and doxorubicin (Adriamycin). Interferon, an immune system stimulator, may be used with chemotherapy. Chemotherapy is effective in about 30 percent of cases and has short-term effects.

External radiation therapy can be administered to decrease tumor size and to decrease the symptoms that the patient is experiencing. Radiation is not effective against liver metastases.

Medications can be used to treat carcinoid syndrome. Octreotide has been effective in reducing the size of some carcinoid tumors. Imodium, lomotil, ondansetran (Zofran), and cyproheptadine (Periactin) may eliminate the diarrhea. Tamoxifen (nolvadex), phenothiazides, gastric histamine receptor antagonists, phentolamine alpha blockers, and corticosteroids may decrease the flushing.

Patients with carcinoid syndrome must take a niacin supplement and ingest adequate protein. Carcinoid tumors use nicotinic acid (a niacin breakdown product) and tryptophan to create serotonin and can deplete the body’s stores of niacin.

Carcinoid cancers are particularly difficult to successfully treat because of the innate ability of many types of this disease to counter targeted treatments. Patients often have to resort to non-targetable drugs such as chemotherapies, which will take both a physical and emotional toll on patients as they work against cancer. In the 2020s, great advancements have been made in the efficacies of immunotherapies, particularly in eliminating the ability of cancers to escape detection and thus survive and thrive.

Prognosis, prevention, and outcomes: With appropriate treatment, a person with carcinoid cancer or carcinoid syndrome can live for ten to fifteen years with a fairly good quality of life. There is no way to prevent carcinoid tumors.

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