Screening should identify cancers at an early stage, before they are clinically evident. Treatment would therefore be more effective, surgery less disfiguring, and there would be a greater likelihood that the cancer will not have spread. To be valid, a screening tool must be easy, convenient, cost-effective, widely available and safe, and it must show a benefit for the participant. With NCI support, the American College of Radiology Imaging Network (ACRIN) has conducted a number of Screening and Interventional Clinical Trials.