The available evidence regarding the efficacy of breast cancer screening by means of periodic mammography in women of 50 years of age or more, is solid and consistent, and is based fundamentally on the results of randomized intervention trials carried out in Canada, the United States, and Europe.
At present, there is no available evidence that screening with mammography, using the proposed techniques and frequency for women of 50 years of age or over, can reduce breast cancer mortality in women of 40 to 49 years of age. Although we do not have direct evidence, we can not exclude the possibility that other more frequent screening modalities may have some effect on the mortality rate in younger women. The interval between tests is a decisive determinant in the cost-effectiveness of breast cancer screening programmes. The additional benefits of changing from a system of mammography every 2 years to a 1 year interval are considered low, while the additional associated costs on attaining these benefits are rather high.
Among the most frequent relevant adverse consequences of screening with mammography are the carrying out of excessive biopsies and other unnecessary diagnostic tests, and the need to return for additional or repeat views.
High-quality mammography is considered an indispensable requisite for a screening programme to be able to reach the objective of a reduction in breast cancer mortality while minimizing the adverse consequences of the massive application of this technique.
Assuring high participation in the screening programmes is a necessary condition for achieving a reduction in the mortality rate for breast cancer in the general population.