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Review
January 11, 1995

Efficacy of Screening MammographyA Meta-analysis

Author Affiliations

From the Department of Epidemiology and Biostatistics (Drs Kerlikowske, Grady, and Ernster, and Mr Sandrock) and the Division of General Internal Medicine, Department of Medicine (Ms Rubin), University of California, San Francisco, and the General Internal Medicine Section, Department of Veterans Affairs Medical Center, San Francisco, Calif (Drs Kerlikowske and Grady).

JAMA. 1995;273(2):149-154. doi:10.1001/jama.1995.03520260071035
Abstract

Objective.  —To determine the efficacy of screening mammography by age, number of mammographic views per screen, screening interval, and duration of follow-up.

Design.  —Literature review and meta-analysis.

Data Identification and Analysis.  —Literature search of English-language studies reported from January 1966 to October 31, 1993, using MEDLINE, manual literature review, and consultation with experts. A total of 13 studies were selected, and their results were combined using meta-analytic techniques based on the assumption of fixed effects.

Main Results.  —The overall summary relative risk (RR) estimate for breast cancer mortality for women aged 50 to 74 years undergoing screening mammography compared with those who did not was 0.74 (95% confidence interval [CI], 0.66 to 0.83). The magnitude of the benefit in this age group was similar regardless of number of mammographic views per screen, screening interval, or duration of follow-up. In contrast, none of the summary RR estimates for women aged 40 to 49 years was significantly less than 1.0, irrespective of screening intervention or duration of follow-up. The overall summary RR estimate in women aged 40 to 49 years was 0.93 (95% CI, 0.76 to 1.13); the summary RR estimate for those studies that used two-view mammography was 0.87 (95% CI, 0.68 to 1.12) compared with 1.02 (95% CI, 0.73 to 1.44) for those studies that used one-view mammography, and for those studies with 7 to 9 years of follow-up, the summary RR estimate was 1.02 (95% CI, 0.82 to 1.27) compared with 0.83 (95% CI, 0.65 to 1.06) for those studies with 10 to 12 years of follow-up.

Conclusion.  —Screening mammography significantly reduces breast cancer mortality in women aged 50 to 74 years after 7 to 9 years of follow-up, regardless of screening interval or number of mammographic views per screen. There is no reduction in breast cancer mortality in women aged 40 to 49 years after 7 to 9 years of follow-up. Screening mammography may be effective in reducing breast cancer mortality in women aged 40 to 49 years after 10 to 12 years of follow-up, but the same benefit could probably be achieved by beginning screening at menopause or 50 years of age.(JAMA. 1995;273:149-154)

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