Medical Decision-Making: To Screen or Not to Screen?

It is commonly believed that screening tests for diseases such as cancer result in better outcomes (i.e., reduced mortality, less aggressive treatment regimens, extended survival). Mammography, colonoscopy, and prostate-specific antigen tests are recommended to detect breast, colorectal, and prostate cancers earlier than clinical symptoms would ordinarily appear. However, as with any treatment protocol, the benefits of screening tests should be evaluated. Randomized screening trials provide the most scientifically credible evaluations of the effectiveness of screening programs for early detection: study participants are offered periodic screening, and those in the control group are told to follow their usual medical care. Evaluating disease-specific mortality rates and other data from screening trials is challenging: trials cannot be blind, and they have contamination from study participants who miss screening exams, control participants who get screened, and screening exams with false-positive and false-negative results. Speakers in this session describe practical issues in evaluating screening, the challenges of conducting large randomized screening trials, new developments in statistical analysis of data from screening trials, and estimating error rates in cancer modalities. They discuss National Cancer Institute trials, the European Randomized Study of Screening for Prostate Cancer, and the Canadian National Breast Cancer Screening Study and implications for public policy and national and global recommendations for cancer screening.