A carcinoid tumor is a tiny growth that can be benign or malignant which grows on the walls of the small intestines and other organs. This tumor develops from enterochromaffin cells, that produce hormones found in the small intestine, colon, rectum, bronchi of the lungs, pancrease, ovaries, testes, bile ducts and appendix. These cells produce a variety of hormones such as histamine, serotonin prostaglandins, dopamine and tachykinins. These cells also produce hormones that have a powerful effect on the circulatory system, lungs, heart and gastrointestinal tract.
Carcinoid syndrome is the symptoms that result from the hormones that are produced and secreted by carcinoid tumors. The symptoms are dependent on the type and quantity of the hormones produced. The most common hormones that are secreted are histamine, chromogranin, serotonin, and bradykinin. The most common symptoms of carcinoid syndrome are diarrhea, abdominal pain, wheezing, valvular heart disease, flushing, and carcinoid crisis - incited by surgery. Carcinoid syndrome occurs in about ten percent of patients with carcinoid tumors.
Carcinoid crisis is a very serious situation that can happen during surgery. Carcinoid crisis can be fatal. The body has a sudden drop in blood pressure, leading to shock, abnormally fast heart rate high blood glucose levels and severe bronchospasm. Patients with carcinoid tumors should be administered somatostatin before the beginning of surgery.
The symptoms of carcinoid tumors are due to the site of the tumor and the type of hormone being secreted. The symptoms are not based on where the tumor may have metastasized to, but where the tumor began. Enterochromaffin cells are found in the digestive tract, the respiratory system, the heptabiliary system and in reproductive glands. The most likely site of the tumor is the lower section of the gastrointestinal system, such as the appendix, rectum and lower sections of the small intestine. Another likely site is the large tubes that connect the windpipe to the lungs called the bronchi.
The classification of carcinoid tumor is neuroendocrine tumors. The tumors are usually slow growing and tumors in a common site may have different characteristics and growth rates.
Carcinoid tumors are categorized by the following set of criteria:
type of hormone produced
growth pattern of the tumor, such as glandular, undifferentiated, trabecular or mixed
site or origin – the ‘fore-gut’, ‘mid-gut’ or ‘hind-gut’
Carcinoid tumors in the GI tract sometimes do not produce symptoms because the hormones released are controlled by the liver. Sometimes the tumors can cause a bowel obstruction, abdominal pain, weight loss and bowel movement changes or fluctuation. GI bleeding can also occur with carcinoid tumors.
Carcinoid tumors can metastasize, usually to lymph nodes, liver, lungs or bone. The probability of metastasis is dependent of the size of the tumor. Tumors less that 1 cm have a 15-25% chance or spreading. Tumors that are 1-2cm have a 58%-80% chance of spreading. For tumors larger that 2cm, the chance of metastasis is over 70%.
Cushing’s syndromes can occur in carcinoid patients. Cushing’s syndrome is the excessive production of hormones from the adrenal glands. Somatostatinoma syndrome is caused by excess production of the hormone somatostatin.
Diagnosis for carcinoid tumors consists of medical imaging, exploratory surgery, urine and blood tests. Sometimes a physician will try to instigate flushing in a patient to help with diagnosis. The drug calcium, gluconate, pentagastrin or alcoholic beverages can instigate flushing for a patient with carcinoid tumors. The test to check for flushing is performed in the hospital so careful observation and monitoring can occur.
Patient’s provide urine samples for a 24 hour period to test for serotonin and its byproducts. Peptides that are at high levels in urine, can also indicate carcinoid tumors. Blood tests are used to measure the levels of peptides and serotonin. Foods that can interfere with the blood and urine test are bananas, eggplant, avocado, and walnuts and they should be avoided for three days before the tests. Drugs which can interfere with the test and should be avoided as well are guaifenesin, acetaminophen, methocarbamol and phenothiazines.
Imaging is used to determine the location of the tumor and whether metastasis has occurred. Tests used could be X-ray, CT scan, MRI scan or a PET scan.
A colonoscopy and an imaging test of the entire GI tract with a barium tracer can be used to detect tumors in the gastrointestinal system. A colonoscopy is an outpatient procedure in which the rectum and colon are examined with a tube that has a light and camera, known as a colonoscope. This procedure is performed under light sedation. A biopsy can be performed during a colonoscopy.
Most carcinoids have receptors for the hormone somatostatin. A radioactive tracer of somatostatin can be injected into the blood stream. Nuclear scanning will then be able to locate the tumor and check its growth and size.
Exploratory surgery is used to locate a suspected tumor, perform a biopsy and determine its stage.
Treatment for carcinoid tumors depends on their stage, malignancy, location and health and age of the patient. Surgery is the most common method for treating tumors. If the tumor is too big or in a difficult location treatment called debulking is used. Debulking is a thinning out of the tumor tissue. Also, when the removal of the tumor is not possible, chemotherapy, radiation therapy and biological therapy are used. If the tumor has spread palliative care is used. Palliative care is focused on maintaining quality of life and controlling pain. Palliative care can involve chemotherapy, radiation therapy and pain medication to alleviate symptoms.
Surgical procedures can involve removal of the whole tumor, removal of the tumor and a part of the organ it is affecting and can be performed using electric current (fulguration) or removal using cryosurgery which involves freezing tissue.
The names for surgical procedures are as follows:
gastrectomy – removal or all or part of the stomach
appendectomy – removal of the appendix
partial hepatectomy – removal of a section of the liver
cecectomy – removal of part of the colon
hemicolectomy – removal of part of the colon and appendix.
Carcinoid tumors that are on the liver or have metastasized to the liver can be surgically treated using hepatic artery ligation or hepatic artery embolization. Hepatic artery ligation is a procedure in which the main artery that supplies the liver is tied off to slow tumor growth. Hepatic artery embolization is a procedure in which drugs or radiation are used to decrease or destroy the flow of blood to the liver and kill the cancer cells.
Chemotherapy that is used to treat carcinoid tumors are used in combination (a cocktail) or singularly and are usually given to the patient through IV. Chemotherapy works in only 30% of patients with metastasized carcinoid tumors for not more than one year. Drugs used are cisplatin, etoposide, doxorubicin or dacarbazine. Side effect of chemotherapy are severe and include fatigue, hair loss, blood anemia, nausea and vomiting.
Biological therapy is also known as immunotherapy. This therapy enhances the body’s immune system to fight the cancer. It can reduce the size of the tumor in up to 17% of patients with carcinoid tumors. Biological therapy can also slow the growth of inoperable tumors and prolong life. Biological drugs are administered via injection and are known as somatostatin analogues, named octreotide, lanreotide and interferon. There are side affects with biological therapy which are cough weakness, anemia, neutropenia and headache.
Radiation therapy is the use of high energy x-rays to kill cancer cells and decrease tumor size. Radiation can be administered from out side of the body or by planting radioactive seeds in the body in or near the tumor. Side effects for radiation therapy are edema, fatigue and skin irritation.
Carcinoids are usually slow growing. The five year survival rate after surgery to remove the tumor is 70 to 90 percent. Forty-five percent of patients diagnosed with carcinoid tumors, have cancer that has already metastasized. Patients with carcinoid tumors that have spread can often live 10 to 15 years after diagnosis. If the tumor has spread to the liver prognosis is poor.
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