Lung cancer is the #1 cancer killer in the U.S., accounting for about 25% of all cancer deaths. The number of lives taken by lung cancer has fallen more than 6% since its peak in 2005, owing to fewer people smoking and to improvements in early discovery through lung cancer screening. While a standard chest X-ray was once used for this purpose, today the Centers for Disease Control and Prevention (CDC) and the US Preventive Services Task Force (USPSTF) recommend only one screening test for lung cancer: Low-dose Computed Tomography, or LDCT.