Is screening mammography effective elderly women?

PURPOSE: Screening mammography is effective in reducing breast cancer morta lity in women between the ages of 50 and 69 years. We sought to determine w hether older women who undergo screening mammography have a decreased risk of metastatic breast cancer. SUBJECTS AND METHODS: We studied 690,993 women aged 66 to 79 years who were California Medicare beneficiaries from January 1992 to December 1993, and who chose the fee-for-service plan. Health Care Financing Administration pa rt B billing records were used to determine the use of screening mammograph y. The extent of breast cancer (in situ, local, regional, or metastatic) wa s ascertained For the 6,767 women who were diagnosed with the disease in 19 93, using data from the California State Cancer Registry. For each type (ex tent) of boast cancer, the relative risk (RR) and 95% confidence (CI) of de veloping breast cancer was estimated by dividing the risk of its developmen t in screened women by the risk in women who were not screened. RESULTS: A total of 46% of women had mammography during the 2-year study pe riod. In situ, local, and regional breast cancer were more likely to be det ected among women who underwent screening mammography. For example, the rel ative risk of detecting local breast cancer in screened women was 3.3 (95% CI: 3.1 to 3.5). The risk of detecting metastatic breast cancer, on the oth er hand, was significantly reduced among women aged 66 to 79 years who unde rwent screening mammography (RR = 0.57, 95% CI: 0.45 to 0.72). CONCLUSION: Screening mammography is associated with a decreased risk of de tecting metastatic breast cancer among elderly women. Public health recomme ndations need to weigh the benefit of screening elderly women against the c ost and potential harm from screening and treating early lesions that may h ave no effect on mortality. (C) 2000 by Excerpta Medica, Inc.