Lung cancer is the most common cause of cancer-related death among both men and women in the United States. Since smoking is the major risk factor for lung cancer and 24% of U.S. adults smoke, lung cancer will continue to be a major problem. 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, computed tomography (computerized x-rays, also called CT scans), or sputum cytologic examination (looking for cancer cells in the fluid that patients cough up). Screening for lung cancer would involve using one of these tests to look for lung cancer in people who have no lung cancer symptoms. In 1996, the USPSTF recommended that doctors not use these tests to screen for lung cancer because studies suggested that the harms were greater than the potential benefits. Since 1996, additional studies have become available.