Lung carcinoid tumors are rare malignant growths that develop from cells that help regulate the flow of air and blood through the lungs. These growths are also known as neuroendocrine lung tumors, pulmonary carcinoids, and lung carcinoids.
Description
These cancers account for 1% to 3% of all lung tumors. Most lung carcinoids measure between slightly less than 1/4" (0.63 cm) and slightly more than 3/4" (1.9 cm). These tumors usually develop in the right lung.
Doctors classify lung carcinoids according to what tumor cells look like under a microscope, and where in the lung the tumor is located. Typical lung carcinoids occur about nine times as often as atypical tumors. They grow slowly and rarely spread beyond the lungs. Atypical lung carcinoids grow somewhat faster than typical tumors and are more likely to spread to other organs. In their most invasive form, atypical lung carcinoids look and behave like small-cell lung cancers.
About 80% of lung carcinoids are central carcinoids. Located in the walls of the large airways in the center of the lungs, where the neuroendocrine cells that form them are most concentrated, these tumors are almost always typical tumors. Carcinoids that develop in the narrower airways, close to the edges of the lungs, are called peripheral carcinoids. Most are typical tumors.
Demographics
Lung carcinoids usually develop between the ages of 45 and 55. These tumors are equally common in men and women and rarely affect children.
Causes and symptoms
Lung carcinoids are not caused by smoking or by exposure to chemicals at work or in the environment.
Doctors believe that central carcinoids develop from glands beneath the surface of the large air passages. Lung biopsies performed to diagnose or treat other conditions sometimes reveal microscopic clusters of neuroendocrine cells. These carcinoid tumorlets look like tiny peripheral carcinoids. They are most common when disease has caused scar tissue to form in the lungs, and may grow to be carcinoid tumors.
Patients who have peripheral or small central carcinoids don't usually show symptoms, but some patients who have central carcinoids cough, wheeze, or cough up blood (hemoptysis).
A large carcinoid that blocks part or all of an airway can cause post-obstructive pneumonia. Doctors may not consider the possibility of a carcinoid until antibiotics fail to cure this lung infection.
About 10% to 20% of lung carcinoids produce hormone-like substances that release into the bloodstream. These substances can cause symptoms such as Cushing's syndrome, acromegaly, or hypercalcemia. They may also cause carcinoid syndrome, which is a constellation of symptoms including facial flushing, abdominal cramps, diarrhea, and breathlessness, among others.
Diagnosis
A thorough physical examination will detect symptoms of syndrome health problems associated with these tumors. If a patient has one or more symptoms that suggest the presence of a lung carcinoid, the doctor will inquire about:
The doctor will use one or more methods to determine whether the patient has a lung tumor. Lung carcinoids that do not cause symptoms usually show up on chest x rays taken during a routine physical or as a result of other health problems.
Chest x rays cannot detect tumors that are very small or hidden by other organs in the chest. A doctor who suspects a lung carcinoid may order additional imaging studies in order to make a more detailed search.
About 75% of lung carcinoids can be seen through a long, lighted tube called a bronchoscope. Doctors also use CT scans, octreoscans, or MIBG (metaiodobenzyl-guanidine) scans to locate lung carcinoids and determine how far they have spread. CT scans provide a detailed view of the lungs. Octreoscans and MIBG scans trace the path of radioactive substances that are attracted to lung carcinoids.
Also called indium-111-labeled DTPA-octreotide scintigraphy, octreoscan involves injecting a small amount of a radioactive hormone-like substance into the patient's vein. Carcinoid tumors attract this substance, and a special camera locates tumors by pinpointing the area where the radioactive material accumulates.
Doctors perform MIBG scans by attaching radioactive iodine to a chemical absorbed by carcinoid tumors. This compound is injected into the patient's bloodstream, drawn to carcinoid tumor cells, and tracked by a special scanner.
Although diagnostic procedures can indicate that a patient might have a lung carcinoid, biopsy is the only way to confirm the diagnosis. Doctors use several different techniques to remove samples of these tumors.
BRONCHOSCOPIC BIOPSY.
To obtain a sample of a tumor in one of the large airways, the doctor uses a bronchoscope to examine the lining of these organs. When a tumor is located, the doctor manipulates pincers or tongs (biopsy forceps) through the bronchoscope to remove a small sample of tissue. The patient leaves the hospital a few hours after undergoing this outpatient procedure. If serious bleeding occurs, the doctor narrows or seals the blood vessels by injecting drugs or aiming a laser beam.
BRUSHING SAMPLE.
A doctor who performs a bronchoscopic biopsy may also wipe a tiny brush over the surface of the tumor. Tumor cells extracted in this way (brushing sample) are examined under a microscope. A
brushing sample can add useful information to the results of bronchoscopic biopsy.
NEEDLE BIOPSY.
Doctors often use needle biopsy to obtain samples of tumors that are not close to the large airways. Guided by a computed tomography scan (CT scan) image, a long needle is passed between the ribs and into the lung to remove a small piece of the tumor. Because carcinoid tumors are usually small, localization using a needle biopsy may be difficult or impossible.
THORACOTOMY.
If neither bronchoscopic biopsy nor needle biopsy yields enough tissue to identify the tumor type, the doctor may open the patient's chest (thoracotomy) to remove a tissue sample. A doctor who feels certain that a tumor is a carcinoid may perform a thoracotomy and remove the entire tumor without having taken a biopsy sample.
Treatment team
Lung carcinoids are treated by thoracic and cardiothoracic surgeons.
Clinical staging, treatments, and prognosis
Staging
Once lung carcinoids have been diagnosed, more tests are done to find out if the cancer has spread from the lung to other parts of the body (staging). A doctor needs to know the stage to plan treatment. Doctors stage lung carcinoids the same way they stage non-small cell lung cancers:
Stage 0: Cancer is only found in a local area and only in a few layers of cells. It has not grown through the top lining of the lung.
Stage I: The cancer is only in the lung, and normal tissue is around it.
Stage II: Cancer has spread to nearby lymph nodes.
Stage III: Cancer has spread to the chest wall or diaphragm near the lung; or the cancer has spread to the lymph nodes in the area that separates the two lungs (mediastinum); or to the lymph nodes on the other side of the chest or in the neck. Stage III is further divided into stage IIIA (usually can be operated on) and stage IIIB (usually cannot be operated on).
Stage IV: Cancer has spread to other parts of the body.
Treatment of lung carcinoids
Doctors consider tumor size and location, and whether the patient has additional lung problems or serious disease affecting any other organ, in order to determine the most appropriate treatment for lung carcinoids.
SURGERY.
Removing the tumor (surgical resection) is the treatment of choice for these cancers because most lung carcinoids:
must be removed in order to prevent airway obstruction and other complications of tumor growth
If the tumor is located in a large airway, the surgeon may remove the tumor and normal tissue above and below it, then sew together the remaining lung tissue. This procedure is a sleeve resection.
If tumor size or location makes sleeve resection impossible, the surgeon removes the affected lobe of the lung (lobectomy). In rare cases, the surgeon removes the entire right or left lung (pneumonectomy).
Surgeons use lobectomy to remove peripheral carcinoids located at the edges of the lungs farthest from the large airways. If the tumor is very small, the surgeon may remove it and a wedge-shaped piece of lung tissue surrounding it (wedge resection).
Surgeons who remove lung carcinoids usually remove some of the lymph nodes near the lungs because:
About 10% of typical carcinoids and 30% to 50% of atypical carcinoids have spread to lymph nodes by the time the disease is diagnosed.
Not removing lymph nodes might increase the risk of cancer spreading to other organs.
Surgery alone cannot cure lung carcinoids that have spread to other organs.
Examining lymph nodes can indicate the likelihood that cancer will recur.
Surgeons who remove lung carcinoids try to preserve the patient's lung function by removing the smallest possible amount of normal lung tissue.
PALLIATIVE TREATMENT.
A patient who has severe emphysema, chronic bronchitis, heart disease, or other medical problems may not be able to withstand the stress of surgery to cure lung carcinoids or to cope with breathing difficulties resulting from removal of normal lung tissue.
Doctors use a bronchoscope and a laser to burn away (vaporize) most of the tumor in a patient who is too ill to withstand surgery. These palliative treatments can relieve most symptoms associated with lung carcinoids, but cannot cure the disease. They are often supplemented by radiation administered externally or directly into the air passages (intrabronchial radiation).
MEDICAL TREATMENTS.
Guidelines issued in 2001 by the National Comprehensive Cancer Network recommend the use of radiation following surgery to remove carcinoid lung tumors, and chemotherapy and radiation following surgery to remove atypical lung carcinoids.
Injected into a vein or taken by mouth, chemotherapy drugs are also used to treat lung carcinoids that have spread to other organs, are causing severe symptoms, or have not responded to other medications. Doctors may combine two or more chemotherapy drugs or add them to other medications to relieve symptoms of lung carcinoids that have spread to other organs.
Octreotide controls wheezing, flushing, and other symptoms of carcinoid syndrome. This medication may temporarily shrink lung carcinoids but does not cure them.
Alpha-interferon can shrink some lung carcinoids that have spread to other parts of the body and relieve symptoms of carcinoid syndrome. Doctors can prescribe other medications to relieve specific symptoms.
Radiation may be an option for patients who are too frail or ill to undergo surgery but is not a very effective treatment for lung carcinoids. High doses of radiation can damage lung tissue, create scar tissue, cause breathing problems, and make the patient more susceptible to infection.
PROGNOSIS.
Five-year survival rates for patients with lung carcinoids are 90% to 100% for typical tumors, and 40% to 76% for atypical tumors. Ten-year survival rates are about 10% lower than five-year rates for both types of tumors. The prognosis is worse for lung carcinoids that measure 1 1/4" (3.2 cm) or larger or have spread to lymph nodes.
Some patients who have had lung carcinoids must continue to have regular x rays and blood tests to help doctors detect recurrent disease in its earliest stages. Any patient who has had a lung carcinoid should notify the doctor whenever new symptoms develop. These symptoms could be side effects of treatment or signs that the disease has recurred. A patient who has recovered from surgery should ask the doctor about an exercise routine to restore energy and reduce shortness of breath.
Clinical trials
Researchers are currently investigating whether:
new methods of delivering radiation can shrink lung carcinoids that have not responded to treatment
inhaling chemotherapy drugs can shrink advanced lung carcinoids
biological therapy can starve lung carcinoids by cutting off the flow of blood that nourishes them and stimulate patients' white blood cells to kill cancer cells
new methods of delivering chemotherapy can kill cancer cells without harming normal cells
new combinations of chemotherapy drugs can prevent cancer cells from multiplying
chemotherapy drugs combined with radioactive substances can locate and kill cancer cells without harming normal cells
Information about clinical trials is available from the National Institute of Health's National Cancer Institute.
Prevention
There are no known risk factors for lung carcinoids, and no methods of prevention are known.
—Hormonal disorder causing progressive enlargement of hands and feet and elongation of the face, headache, muscle pain, and visual and emotional disturbances in middle-aged men and women.
Carcinoid syndrome
—Rare malignant disease characterized by facial flushing, abdominal cramps, diarrhea, breathlessness, and other symptoms. Affects fewer than 10% of patients with carcinoid tumor.
Cushing's syndrome
—Hormonal disorder characterized by a round face, mental or emotional instability, high blood pressure, weight gain, or abnormal growth of facial and body hair in women.
Emphysema
—Abnormal lung condition characterized by breathing problems, cough, rapid heartbeat. Later stages are characterized by restlessness, weakness, confusion, increased breathlessness, and may cause fluid to collect around the lungs (pulmonary edema) and congestive heart failure.
Hypercalcemia
—Abnormally high levels of calcium in the blood, causing muscle pain and weakness and loss of appetite. Severe cases can result in kidney failure.
QUESTIONS TO ASK THE DOCTOR
What kind of lung carcinoid do I have?
What treatment do you recommend?
Will this treatment cure me?
What can I do to make this treatment more successful?
