Lung cancer is the most common cause of cancer-related death among men and women in the United States. Lung cancer is difficult to treat unless it is found at very early stages. Unfortunately, most people do not develop symptoms until the cancer has spread. Symptoms include cough, spitting up blood, weight loss, and difficulty breathing. Tests that can detect lung cancer before patients have symptoms include chest x-rays and computed tomography (computerized x-rays, also called CT scans). Screening for lung cancer would involve using one of these tests to look for lung cancer in persons who have no symptoms. However, no studies to date have proven that screening helps people live longer. In addition, these tests expose patients to radiation and often have false-positive results. False-positive test results mean that the test shows an abnormality that turns out not to be cancer; such results can lead to unnecessary worry, testing, and surgery.