Study questions benefits of breast cancer screenings as practiced in the real world

Jul 20 2005

A new study calls into question the actual benefits of breast cancer screenings as practiced in the real world, as opposed to the well-controlled situations of previous screening trials. The study appears in the July 20 issue of the Journal of the National Cancer Institute.

During the past two decades, many organizations have recommended regular breast cancer screenings for women, leading to the widespread adoption of mammography and clinical breast examination screenings. However, the basis of these recommendations comes from data produced in carefully controlled research studies. Thus, controversy has arisen concerning the true benefit of mammography in real-world situations.

To address this question, Joann G. Elmore, M.D., M.P.H., of the University of Washington in Seattle, and colleagues reviewed the medical records of 1,351 ethnically diverse women from around the United States who had died from breast cancer between 1983 and 1998. They compared this information to data from a control group of 2,501 cancer-free women, matched for age and risk factors (e.g., family history). If screening for breast cancer really does prevent women from dying of the disease, the women still living would have had more screenings, the authors reasoned.

However, they found very similar screening rates among the groups. For example, 69.7% of the cancer patients aged 50-65 years with an average risk of developing the disease had gotten mammograms and/or breast examinations by a clinician, compared with 69.2% of the cancer-free women of similar age and risk.

Among women with an increased risk of the disease, the authors did see a 26% reduction in breast cancer mortality associated with screenings, but this was not statistically significant. "We observed no appreciable association between breast cancer mortality and screening history," regardless of age or risk-level, the authors ultimately concluded.

Because older carefully controlled breast cancer screening trials suggested that periodic screenings may reduce breast cancer mortality, the authors suggest several reasons for the discrepancy between their results and prior studies, and they urge caution when interpreting their study's results. For example, the authors could only gain limited amounts of information from clinical records and retrospective data. However, the quality of community screening may not be the same as that of a research trial, and the development of new life-saving treatments for breast cancer may have improved survival rates regardless of screening history, the authors point out.

In an accompanying editorial, Russell Harris, M.D., M.P.H., of the University of North Carolina, Chapel Hill, suggests that issues that may reduce the effectiveness of formal screenings in real-life situations include problems with implementing screening programs in real-world communities and recent improvements in the detection and treatment for breast cancer patients. Also, the fact that many women are now seeking medical care for small lumps found in self-examinations may make screening less useful than it once was. "We need to recognize when issues of implementation … are limiting the effectiveness of our interventions. And we need to recognize when … a previously effective intervention (is) no longer useful," he concludes.