Scientists say cholesterol-lowering drugs called statins may protect against the development of lung cancer.  In a study appearing this month in the journal Chest, researchers report that statin use of six or more months was associated with a 55 percent reduction in risk for lung cancer. Risk dropped for all age groups-regardless of race, smoking status or body-mass index. The study is significant because it involved a very large group. Researchers from Louisana State University and the Overton Brooks V.A. Medical Center in Shreveport, La., studied more than 480,000 patients enrolled in the Veterans Administration Health Care System over a six-year period. Lung cancer is the most lethal form of the disease in the United States.