[The relationship between health gain and effort in mass screening for breast cancer]

Mass screening for breast cancer reduces the mortality of this disease. In the Netherlands, with a very high incidence of breast cancer, a well organized health care system and a stable economic prosperity, the decision taken to implement nationwide breast cancer screening for the female population aged 50-70 years appears well-founded. The first data indeed suggest a reduction of breast cancer in the coming years. The effects of screening as such will be difficult to evaluate since the programme leads also to optimalization of breast cancer treatment in general. Other factors, such as adjuvant therapy, may have a beneficial effect on breast cancer mortality, reducing the yield of the screening proper. This and the non-negligible negative aspects should not be hidden from the public. Continuous evaluation and quality control, not only in mammography techniques and reading, but also in the treatment of the detected cases, are essential for a successful screening programme.