Lung cancer produces such quiet symptoms in its early stages that it is typically diagnosed at an advanced stage. Later in the disease, people often notice fatigue, poor appetite, and unexplained weight loss. These symptoms are common in many forms of cancer.
Lung cancer symptoms specific to its growth and spread may include coughing up red or rust-colored phlegm, wheezing, and shortness of breath. Sometimes an infection in the lung behind the tumor that is obstructing the airway produces a fever. Invasion of cancerous cells into the pleura (membrane covering the lungs) or other nearby structures can produce pain in the chest, shoulders, or arms.
If the cancer spreads to surrounding tissues, it can lead to enlarged lymph nodes in the chest or neck and impingement of various nerves, resulting in hoarseness. Because of a narrowing of the esophagus, a person may have difficulty swallowing. There may be swelling of the neck and face from blockage of blood flow from these areas to the heart. In up to 30 percent of patients, lung cancer also causes clubbing of the fingers.
Lung cancer often spreads to the liver and bone marrow, where it can interfere with blood cell formation. When it spreads to the bones, it causes pain and fractures; and when it spreads to the brain, it produces neurological symptoms such as seizures.
Some lung cancer patients with small cell tumors develop Cushing’s syndrome, which produces complications such as osteoporosis, hypertension, and face roundness. Another potential complication of lung cancer is hypercalcemia. In this condition, excessive blood levels of calcium can cause fatigue, muscle weakness, confusion, drowsiness, and coma.
In some cases, cancer is discovered in people with no lung cancer symptoms, usually when they have a chest X-ray for another reason. The majority of lung cancers, however, are diagnosed after a doctor requests testing for cancer based on a patient’s medical history and the results of a physical examination.
Doctors have not recommended general screening for lung cancer in at-risk individuals (smokers and former smokers) because a standard chest X-ray is not sensitive enough to locate small tumors, and studies have shown that two screening methods—chest X-rays and phlegm examinations—do not decrease deaths from lung cancer.
More recently, studies have shown that low-radiation-dose spiral computed tomography (spiral CT), also known as low-dose CT, has value as a screening tool for lung cancer for people at high risk for the disease. 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 low-dose CT sponsored by the National Cancer Institute found 20 percent fewer lung cancer deaths among current and former heavy smokers screened with low-dose CT compared with chest X-ray.
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 a person who is suspected of having lung cancer. But 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 studies—CT, magnetic resonance imaging (MRI), and positron emission tomography (PET) scans—are important components of this evaluation.