Background: The risks and benefits of mammography screening among women 40 to 49 years of age remain an important issue for clinical practice.

Purpose: To evaluate the evidence about the risks and benefits of mammography screening for women 40 to 49 years of age.

Data sources: English-language publications in MEDLINE (1966-2005), Pre-MEDLINE, and the Cochrane Central Register of Controlled Trials and references of selected studies through May 2005.

Study selection: Previous systematic reviews; randomized, controlled trials; and observational studies.

Data extraction: Two independent reviewers.

Data synthesis: In addition to publications from the original mammography trials, 117 studies were included in the review. Meta-analyses of randomized, controlled trials demonstrate a 7% to 23% reduction in breast cancer mortality rates with screening mammography in women 40 to 49 years of age. Screening mammography is associated with an increased risk for mastectomy but a decreased risk for adjuvant chemotherapy and hormone therapy. The risk for death due to breast cancer from the radiation exposure involved in mammography screening is small and is outweighed by a reduction in breast cancer mortality rates from early detection. Rates of false-positive results are high (20% to 56% after 10 mammograms), but false-positive results have little effect on psychological health or subsequent mammography adherence. Although many women report pain at the time of the mammography, few see pain as a deterrent to future screening. Evidence about the effect of negative screening mammography on psychological well-being or the subsequent clinical presentation of breast cancer is insufficient.

Limitations: Few randomized, controlled trials assessed the risks of screening, and the literature search was completed in 2005.

Conclusions: Although few women 50 years of age or older have risks from mammography that outweigh the benefits, the evidence suggests that more women 40 to 49 years of age have such risks.