The main expected benefit of breast cancer screening is lower mortality. Earlier detection of these cancers may lead to less strenuous treatments and to the possibility to use breast-saving interventions; the need for treatment resources may thus decrease compared to treating more advanced stages of cancer. Knowing that no breast cancer has been detected may improve the quality of life of screened persons. The disadvantages include false positive screening results that cause worry and extra cost for follow-up tests. False negative test results and added medical radiation by screening may increase mortality.
Estimates of the effects of screening vary considerably in the literature. Although several large studies have been completed, the relatively small number of women dying in breast cancer makes it difficult to show the exact changes in mortality. Another difficulty is separating the independent effect of screening from the mortality decrease caused by recent improvements in treatment. The screening-induced increase in life expectancy is also technically demanding to separate from increases due to other factors, such as changes in general health in successive cohorts of women.
In the basic estimate, we used the following elements for Finnish women between 60 and 69 years of age (n=256 000): mammography screening every two years, participation in screening 85%, mortality decrease 25% among women who participate in screening, mean increase in life expectancy 10 years for women with breast cancer found by screening, and cost per mammography 200 FIM. The number of new breast cancers in this age group was set to 700 and ten-year mortality at 40%. For eventual extension of mammography screening, Finland has a sufficient number of screening devices and professionals experienced in screening; however, their geographical distribution is uneven. Some municipalities will need notable extra resources to extend screening into new age groups, while others can manage with their existing arrangements.