Mammography is of little benefit in women younger than 50 years of age
ACP J Club. 1996 Jan-Feb;124:14. doi:10.7326/ACPJC-1996-124-1-014
Glasziou PP, Woodward AJ, Mahon CM. Mammographic screening trials for women aged under 50. A quality assessment and meta-analysis. Med J Aust. 1995 Jun 19;162:625-9.
To determine the benefit of mammography in women < 50 years of age.
Studies were identified using MEDLINE searching for primary articles, reviews, and meta-analyses; by searching for authors known to be participating in screening trials; and by reviewing bibliographies of relevant articles.
Selected studies were randomized controlled trials of breast cancer screening that included women aged < 50 years. 7 trials that included 159 465 women with 8 to 9 years of follow-up met inclusion criteria.
2 assessors, blinded to trial results and identifying information, extracted the method of randomization, comparability of baseline data, standardized criteria for death from breast cancer, cause of death, completeness of follow-up, and use of an intention-to-treat analysis. A combined relative risk (RR) for breast cancer death was calculated.
The screening method included physical examination and mammography (3 trials) or mammography alone (4 trials). Blinded assessment of cause of death was present in only 3 of 7 trials. The combined estimated RR for death from breast cancer was 0.95 (95% CI 0.77 to 1.18, P = 0.64). A test for heterogeneity showed that no significant differences existed among results of the 7 studies. A sensitivity analysis tested the effects of the design and conduct of the trials on the overall results. Adjustment for the cluster randomization used by 2 trials (47 171 patients) did not appreciably alter the results (RR 0.95, CI 0.76 to 1.18), nor did adjustment for compliance (RR 1.0, CI 0.74 to 1.35), nor use of a random-effects model (RR 0.95, CI 0.77 to 1.18). The trials were similar for quality of radiologic screening as judged by the sensitivity for detection of breast cancer.
The benefit of mammographic screening is small or nonexistent in women younger than 50 years of age.
Source of funding: In part, National Programme for the Early Detection of Breast Cancer.
For article reprint: Dr. P. Glasziou, Department of Social and Preventive Medicine, University of Queensland Medical School, Herston Road, Herston, Queensland 4006, Australia. FAX 61-7-3365-5442.
The controversy over mammographic screening for breast cancer in younger women continues to rage. This timely and rigorous meta-analysis adds to the growing body of evidence that no significant survival benefit exists for mass screening mammography in women < 50 years of age (1-3). 7 large trials, individually or collectively, did not show a significant decrease in breast cancer mortality associated with screening.
This meta-analysis specifically addresses issues that are used by proponents of early mammography to support their position. For example, compliance and mammogram sensitivity did not explain differences in the results of the trials, nor did consideration of these factors change the results of the meta-analysis.
This meta-analysis further bolsters the assertion that the survival benefit of mass screening mammography is quite small or nonexistent in women < 50 years of age. Clinicians, however, should continue to consider specific patient risk factors and preferences in their decision-making process for individual patients.
Laura Willett, MD
Robert Wood Johnson Medical SchoolNew Brunswick, New Jersey, USA