Age-specific effectiveness of the Finnish cervical cancer screening programme.

BACKGROUND: There is currently some uncertainty about the effectiveness of screening outside the established core ages of 30 to 60. We audited the screening histories of cervical cancers and conducted a case-control evaluation of the effectiveness of organized screening in different ages.
METHODS: Screening histories for 1,546 cervical cancer cases and 9,276 age-matched controls were derived by linkage to the screening register. ORs and 95% confidence intervals (CI) for the association of participation in a program screen and cervical cancer diagnosis in the following screening interval were estimated using conditional logistic regression and corrected for self-selection bias.
RESULTS: Participation in a single screen was associated with a 47% decrease in cervical cancers, but this effect was age-dependent. Screening at 25 showed little or no impact on the risk of cervical cancer in the next interval, whereas screens at 40 to 65 showed protective effects of 51% to 66%.
CONCLUSIONS: Program screening at the age of 25 is not associated with a reduced risk of cervical cancer in the following screening interval. Additional analyses are needed that also take opportunistic screening of women during the first rounds of organized screening into consideration. In contrast, screening yields substantial risk reductions in older ages at least up to the age of 60. This study also provides moderate indication of a long-lasting risk reduction associated with screening at the age of 65. IMPACT: Cervical cancer screening effectiveness is for the first time evaluated at different ages up to 65 with correction for self-selection bias of participation in organized screening. ©2012 AACR.