Higher Detection Rates of Biologically Aggressive Breast Cancers in Mammography Screening than in the Biennial Interval.

Purpose Assessment of age group-dependent detection rates of invasive breast cancers among participants in mammography screening including the interval, classified into immunohistochemical subtypes indicating the intrinsic tumor aggressiveness. Materials und Methods The target population comprises women aged 50 - 69 years. All invasive breast cancers diagnosed in one screening (sc) unit during the implementation phase 1/2006 - 12/2010 or identified by the cancer registry during the biennial interval (iv) were categorized based on hormonal-receptor status (HR) and Her2-expression (Her2) into the following subtypes: a) HR+ Her2-, b) HR+ Her2+, c) HR-Her2+ or d) HR- Her2- (triple-negative); Her2+ and triple-negative types were defined as aggressive. The calculated detection rates (DR, parts per thousand) were based on 53 375 sc-examinations and for the interval on 52 887 sc-negative examinations. Results The DRs of all subtypes were higher in screening versus the interval: (a) 4.95 parts per thousand (n = 264) vs. 1.00 parts per thousand (n = 53); b) 0.92 parts per thousand (n = 49) vs. 0.25 parts per thousand (n = 13); c) 0.36 parts per thousand (n = 19) vs. 0.06 parts per thousand (n = 3); d) 0.39 parts per thousand (n = 21) vs. 0.19 parts per thousand (n = 10). 77.4 parts per thousand (89/115) of all aggressive breast cancers including the following 2-year interval were diagnosed by screening. The sum of the DR of aggressive cancers was 1.67 parts per thousand in screening and 0.49% in the interval; the corresponding DRs for women aged 60 - 69 years [sc: 2.24 parts per thousand (51/22 814), iv: 0.58 parts per thousand (13/22 536)] were higher than among women aged 50 - 59 years [sc: 1.24 parts per thousand (38/30 561), iv: 0.43 parts per thousand (13/30 351)]. Conclusion Screening has the potential for earlier diagnosis of aggressive tumor types as its detection rate is about three-fold higher compared to the interval. Within the target group, participants aged 60 - 69 years are at risk based on absolute numbers. They show a nearly two-fold higher detection rate of Her2-positive or triple-negative tumors compared to the age group 50 - 59 years.