Effectiveness of population-based service screening with mammography for women ages 40 to 49 years: evaluation of the Swedish Mammography Screening in Young Women (SCRY) cohort.
BACKGROUND
The effectiveness of mammography screening for women ages 40 to 49 years still is questioned, and few studies of the effectiveness of service screening for this age group have been conducted.


METHODS
Breast cancer mortality was compared between women who were invited to service screening at ages 40 to 49 years (study group) and women in the same age group who were not invited during 1986 to 2005 (control group). Together, these women comprise the Mammography Screening of Young Women (SCRY) cohort, which includes all Swedish counties. A prescreening period was defined to facilitate a comparison of mortality in the absence of screening. The outcome measure was refined mortality, ie, breast cancer death for women who were diagnosed during follow-up at ages 40 to 49 years. Relative risks (RRs) with 95% confidence intervals (CIs) were estimated.


RESULTS
There was no significant difference in breast cancer mortality during the prescreening period. During the study period, there were 803 breast cancer deaths in the study group (7.3 million person-years) and 1238 breast cancer deaths in the control group (8.8 million person-years). The average follow-up was 16 years. The estimated RR for women who were invited to screening was 0.74 (95% CI, 0.66-0.83), and the RR for women who attended screening was 0.71 (95% CI, 0.62-0.80).


CONCLUSIONS
In this comprehensive study, mammography screening for women ages 40 to 49 years was efficient for reducing breast cancer mortality.
Hellquist
Barbro Numan
BN
Department of Radiation Sciences, Umeå University, Umeå, Sweden. barbro.numan@oc.umu.se
Duffy
Stephen W
SW
Abdsaleh
Shahin
S
Björneld
Lena
L
Bordás
Pál
P
Tabár
László
L
Viták
Bedrich
B
Zackrisson
Sophia
S
Nyström
Lennarth
L
Jonsson
Håkan
H
D000328:Adult; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000401:mortality / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D006078:Government Programs; D006801:Humans; D008327:Mammography; D008403:Mass Screening; D008875:Middle Aged; D013548:Sweden