Potential contribution of screening to cancer mortality reduction.

The objective of screening for cancer is to reduce mortality or to improve quality of life. Screening is practiced for several anatomical sites and by several tests. Only cervical cancer screening based on cytological smears has been shown to be effective as a public health policy. Screening for breast cancer based on mammography was shown to reduce mortality in several randomized trials and nonexperimental studies. However, no data are available on its effectiveness at population levels in terms of a public health policy. There are several other valid tests. Application of these tests has failed to demonstrate a reduction in mortality or such an application was never tried and tested. This emphasizes that the prerequisite for effective screening is that the total program is valid and not only the test. At present, knowledge on screening is not fully applied in most European countries. Regular screening for cervical cancer will result in a 90% reduction in the risk of invasive disease. It is likely that the protective effect for breast cancer is about 30%. At the population level, smaller protections are to be expected, and well-organized screening programs are likely to reduce the total cancer death rate by 6 to 10% among females.