Diagnosis of Lung Cancer
Approximately 10 percent of lung cancers are discovered in people with no symptoms, usually when they have a chest x-ray for another reason. However, the majority of lung cancers are diagnosed after a doctor requests testing for cancer based on a patient's medical history and the results of a physical examination.
Doctors usually do not recommend general screening for lung cancer in at-risk individuals (smokers and former smokers). That is because a standard chest x-ray is not sensitive enough to locate small tumors, and studies have shown that two screening methodschest x-rays and phlegm examinationsdo not decrease deaths from lung cancer.
A new technology known as low-radiation-dose spiral computed tomography (spiral CT scan) is currently being investigated as a screening tool for lung cancer. Spiral CT generates a series of cross-sectional images of the lungs that are used to create a three-dimensional image.
Recent results from a multicenter study of spiral CT sponsored by the National Cancer Institute found 20 percent fewer lung cancer deaths among study participants screened with CT compared with chest x-ray. This type of screening is not appropriate for all smokers. Ask your doctor whether the benefits outweigh the risks in your case.
A tissue biopsy is essential for an accurate diagnosis of lung cancer. Biopsy results also guide treatment decisions. A biopsy sample can be obtained from the suspicious area through a bronchoscope, a thin, flexible tube passed through the windpipe and into the bronchial passage. Tissue is obtained directly from an airway or by passing a needle through an airway into adjacent tumor tissue.
Alternatively, needle biopsy through the chest wall, guided by a CT scan, may be used to obtain tissue from a suspicious growth within the lung.
In general, a positive result from a lung cancer test is unlikely to be false in an individual who is suspected of having lung cancer. However, a negative result does not necessarily exclude cancer, and further testing is often necessary. Tests may include an open lung biopsy or a mediastinoscopy, examination of the structures behind the breastbone. The sites where cancer commonly spreads, such as the lymph nodes, bone marrow, and pleura, also are suitable areas for biopsy.
Staging, which determines how much cancer is present and how far it has spread, guides treatment decisions. Imaging studiesCT, magnetic resonance imaging (MRI scan), and positron emission tomography (PET) scansare important components of this evaluation.