A doctor who suspects lung cancer can use a variety of tests to diagnose the disease. Other tests are used to see whether the cancer has metastasized (spread to other parts of the body). Here are some of the tests commonly used in diagnosing and staging lung cancer:
X-rays: Your doctor may order a regular chest X-ray to look for any abnormal areas in the lungs that might be cancer. This is usually the first test a doctor will use if lung cancer is suspected. However, it generally is not sensitive enough to detect small tumors, so doctors often prescribe other imaging tests as well.
CT (computed tomography) scan: This special kind of X-ray can better visualize tumors in the lungs. This scan is sometimes used to see whether a cancer has spread to other organs in the body. It may be combined with another kind of imaging test called a PET (positron emission tomography) scan to get a more complete picture. A CT scan generally costs more than a standard chest X-ray and exposes patients to slightly more radiation.
MRI (magnetic resonance imaging): This imaging test provides clear pictures but takes longer to perform than a CT scan or an X-ray and is considerably more expensive. It generally is used not to diagnose lung cancer but to help doctors figure out how extensive a lung cancer has become.
Bone scans: These may be used if cancer is diagnosed and doctors want to see whether it has metastasized to the bones. But newer imaging techniques, like the PET scan, are proving to be just as effective as bone scans.
Examination of cells: Cells obtained from sputum (mucus coughed up from the lungs) are examined under a microscope to see whether they contain cancer cells.
Fiber-optic examination: Under anesthesia, a tiny camera attached to a thin, flexible fiber-optic tube is inserted into the bronchial passages of the lungs to look for tumors or lesions. In some centers, these examinations have been enhanced with the addition of an ultrasound probe attached to the camera to give an even more complete picture of the tumor and the chest anatomy.
Biopsy: In these procedures, a small sample of cells removed from a suspicious growth in the lungs is examined under a microscope to see whether it contains cancer cells. The tissue is generally taken one of three ways. In one procedure, a tubelike device called a bronchoscope is passed through the nose or mouth into the windpipe and then lungs. The sample is obtained through a needle inserted into the suspicious growth. Alternately, the sample may be obtained through the chest wall by a biopsy needle guided by CT imaging. You are sedated during both these procedures. Thirdly, you may need to have general anesthesia and undergo surgery. These days this is normally done through very small incisions in your neck or chest wall with the surgeon using a tiny camera and small instruments.
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Lung cancer is such a serious disease because most cases are found only in the late stages of the disease, when treatments aren't often very effective. So researchers are eager to find some kind of test that could be given to people with no symptoms but who fit a certain risk profile. An example of people at higher-than-average risk for lung cancer would be older individuals who smoked for many years. Some of the tests used to diagnose the disease have also been proposed as potential screening tests, but so far they haven't proved to effectively find cancers at an early enough stage that they can be successfully treated.
Now researchers are studying the benefits of screening the highest-risk patients with a special imaging scan called a spiral CT. This test, which takes about 20 seconds and exposes patients to a little more radiation than a standard X-ray, generates a three-dimensional image. The smallest lesion that can be spotted in a standard X-ray is about the size of a marble, which would contain a billion cancer cells. It takes about ten years for a lung cancer to grow that large.
The downside to a spiral CT scan is that it can't distinguish between a small lung cancer that's on the move and a harmless nodule or a tumor that is so slow growing that it poses little risk to health. In fact, 95 percent of the "spots" or suspicious-looking areas that show up on the CT scan are benign; only about 3 percent turn out to be cancerous tumors. For most people, then, the scan results in unnecessary, expensive, and sometimes risky diagnostic procedures as well as a lot of worry.
A large study to examine the potential benefits of a spiral CT screening program is underway, but full results aren't due for several years. Some people may want to have the test anyway, though it hasn't been proved to increase survival and could lead to unnecessary biopsies or other procedures.
Lung cancers are classified as small cell lung cancer and non-small cell lung cancer, depending on how the cancerous cells look under a microscope. Your doctor will order tests to determine which type of cancer you have because this will determine how it will be treated.
Non-small cell lung cancer is the most common type and includes:
- Squamous cell carcinoma: Also known as epidermoid carcinoma, this type of cancer begins in the squamous cells of the lungs. It is most often associated with a history of smoking.
- Adenocarcinoma: This type begins in the cells lining the lung and occurs more frequently than other types in nonsmokers, women, and younger people.
- Large cell carcinoma: This type has larger cells than do others.
Small cell lung cancer grows more rapidly and is more likely to spread quickly to other organs. It's also known as oat-cell cancer.
Mesothelioma is a rare tumor of the lining of lungs, often attributed to asbestos exposure.
Lung carcinoid tumors are very rare and typically more benign.
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This type of tumor is considered separately from other lung cancers. It is rare—there are only about 1,700 cases of this cancer a year, according to the American Cancer Society. These growths arise from specific cells responsible for secreting hormones like adrenaline. Most often, carcinoid tumors are found in the gastrointestinal tract, but they can also be found in the lungs. Typical carcinoids grow very slowly, while atypical carcinoids grow marginally more quickly.
Both have relatively good prognoses, especially compared with other types of lung cancer. The ACS says that the five-year survival rate for people with typical lung carcinoids is about 95 percent and that the rate is about 70 percent for people with atypical lung carcinoids. Most are cured with surgery. Chemotherapy and radiation are used primarily in the rare cases where the cancer has spread or cannot be removed surgically.
Some of the tests used to diagnose lung cancer are also used to "stage" it, or determine the degree to which it has spread. Treatment and prognosis will depend on the stage of the cancer. Staging varies by the type of lung cancer.
- Small cell lung cancer: SCLC has two stages, limited and extensive. Limited SCLC is confined to one side of the chest and to nearby lymph nodes. Extensive SCLC means that the tumor has spread to the other lung, to other parts of the body, or to lymph nodes on the opposite side of the chest.
- Non-small cell lung cancer: The NSCLC staging system factors in the primary tumor, local lymph nodes, and other organs to which the cancer might have spread. It uses a numerical scale, ranging from "early stage" (or Stage I, in which the cancer is confined to the lung only, and Stage II, in which the cancer has spread to nearby lymph nodes or the chest wall, diaphragm, tissue surrounding the heart, or membrane covering the lungs) to "locally advanced disease" (Stage III, in which the cancer spreads to lymph nodes between the lungs or the opposite side of the chest or neck) and "metastatic disease" (or Stage IV, in which the cancer has spread to other areas of the body or the other side [or lobe] of the lungs).
Last reviewed on 7/28/09
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