Benefits and harms of mammography screening

Breast Cancer Research

Table 2 Different percentages of overdiagnosis and mortality reduction based on the number of cancers overdiagnosed and deaths avoided from breast cancer using different denominators (incidence/death from breast cancer in different age-groups) in Norway in 2010

Age (years)	Expected number of cancers	Percentage of overdiagnosis (n = 714.4)	Expected number of breast cancer deaths	Percentage of mortality reduction (n = 53.7)
50-99	2,208	19.4	693	7.8
50-79	1,571	27.3	506	10.6
50-69	942	45.5	334	16.1

The expected number of breast cancers and breast cancer deaths is estimated as the observed incidence and mortality rates in Norway from 1980 to 1984 multiplied by the Norwegian female population in 2010 [45-47]. The number of overdiagnosed cancers (714.4 cancers) is based on studies by Falk and coworkers [45] and Kalager and coworkers [44] and the number of reduced breast cancers (53.7 avoided deaths from breast cancer) is estimated by reducing the number of expected (358) breast cancer deaths by 15% in the age group 55 to 74 years (358 × 0.15 = 53.7).

ISSN: 1465-542X