The impact of the U.S. Preventive Services Task Force guidelines on cancer screening: perspective from the National Cancer Institute. The U.S. Preventive Services Task Force evaluated the medical literature, utilizing strict criteria to judge the merits of experimental trials designed to show benefit in screening for cancer. For individuals at normal risk, the task force was not able to make recommendations for or against screening for colorectal, prostate, skin, oral, or testicular cancers. Only one physical-examination cancer-screening procedure has ever been tested in a randomized trial. During the past 27 years, the National Cancer Institute (NCI) has funded six randomized screening trials. Thus far, only one has shown a decrease in mortality. Recognizing the limitations of such trials, the NCI published "Working Guidelines for Early Cancer Detection." Designed for the practicing physician, these guidelines were based upon the best available evidence and on the judgment of representatives of medical professional organizations. 