Meta-analysis of breast cancer mortality benefit and overdiagnosis adjusted for adherence: Improving information on the effects of attending screening mammography

Gemma Jacklyn*, Paul Glasziou, Petra Macaskill, Alexandra Barratt

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

15 Citations (Scopus)


Background: Women require information about the impact of regularly attending screening mammography on breast cancer mortality and overdiagnosis to make informed decisions. To provide this information we aimed to meta-analyse randomised controlled trials adjusted for adherence to the trial protocol. 

Methods: Nine screening mammography trials used in the Independent UK Breast Screening Report were selected. Extending an existing approach to adjust intention-to-treat (ITT) estimates for less than 100% adherence rates, we conducted a random-effects meta-analysis. This produced a combined deattenuated prevented fraction and a combined deattenuated percentage risk of overdiagnosis.

Results: In women aged 39-75 years invited to screen, the prevented fraction of breast cancer mortality at 13-year follow-up was 0.22 (95% CI 0.15-0.28) and it increased to 0.30 (95% CI 0.18-0.42) with deattenuation. In women aged 40-69 years invited to screen, the ITT percentage risk of overdiagnosis during the screening period was 19.0% (95% CI 15.2-22.7%), deattenuation increased this to 29.7% (95% CI 17.8-41.5%).

Conclusions: Adjustment for nonadherence increased the size of the mortality benefit and risk of overdiagnosis by up to 50%. These estimates are more appropriate when developing quantitative information to support individual decisions about attending screening mammography.

Original languageEnglish
Pages (from-to)1269-1276
Number of pages8
JournalBritish Journal of Cancer
Issue number11
Publication statusPublished - 24 May 2016


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