Mammography screening backed by task force
Women age 40 and older should have a mammogram every one to two years, with or without clinical breast examination, to screen for breast cancer, according to new guidance from the U.S. Preventive Services Task Force.
The task force, which systematically reviews the evidence of effectiveness of a wide range of clinical preventive services, published two earlier breast cancer-screening recommendations that endorsed mammography for women older than age 50. The panel now is extending that recommendation to all women older than age 40, but found that the strongest evidence of benefit and reduced mortality from breast cancer is among women ages 50-69.1
The recommendation acknowledges that there are some risks associated with mammography, such as false-positive results that lead to unnecessary biopsies or surgery, but that these risks lessen as women get older. Women should discuss their personal preferences with their clinicians to determine when they should have their first mammogram and how often to have the screening procedure, says Janet Allan, PhD, RN, professor and dean at the University of Texas Health Science Center at San Antonio School of Nursing and vice chair of the task force.
"I think the task force’s position is that we want women to be as informed as possible when making choices about this," she says. "And we do think that women have choices here."
Balance risks, benefits
Screening for breast cancer, the most common form of cancer in women in the United States, poses potential benefits and harms. While studies of mammography have limitations, the task force concluded there was fair evidence that mammography screening every one to two years could reduce breast cancer mortality by approximately 20%-25% over 10 years. While the evidence was strongest for women ages 50-69, the panel concluded benefits were likely to extend to women ages 40-49. (The task force’s breast cancer screening recommendation and materials for clinicians and patients are available on the web at www.ahrq.gov/clinic/3rduspstf/breastcancer/.)
The Bethesda, MD-based National Cancer Institute also has reaffirmed its support of mammography screening. It continues to recommend that women in their 40s should be screened every one to two years with mammography, as should women age 50 and older. Women who are at higher-than-average risk of breast cancer should seek expert medical advice about whether they should begin screening before age 40 and how frequently to be screened.
In addition to age, other factors may increase a woman’s risk of breast cancer. The strongest risk factors are a family history of breast cancer in a mother or sister, having already been diagnosed with breast cancer, or having had a previous breast biopsy showing atypical hyperplasia, an irregular pattern of cell growth.2
Review spurs debate
An October 2001 critique of seven clinical trials of mammography done in the 1960s through the 1980s questioned the benefit of the procedure and fueled an ongoing scientific debate on the subject.3 The ensuing coverage in the popular press about the ongoing scientific dialogue generated news stories that may have been misunderstood or provoked anxiety among patients, says Carolyn Runowicz, MD, vice chairwoman of the department of obstetrics and gynecology at St. Luke’s-Roosevelt Hospital Center in New York City.
It is important that clinicians make it clear that the recent "media hype" was not about new data, stresses Runowicz. The members of the review group decide to re-review the clinical trials on mammography; based on their selected criteria, all but two of the trials were included, she adds.
"Based on a review of this very selected data, they concluded that mammography may not save as many lives as we have believed," states Runowicz. "However, this was a selective review and not new data."
Screening saves lives
Based on early detection and improved therapies, scientists are seeing a decline in mortality attributable to breast cancer, says Runowicz. Research is indicating that the earlier cancer is detected, the more likely it is to be in an early stage, which is associated with an improved survival rate, she notes.
The National Cancer Institute continues to address the uncertainties surrounding screening mammograms by monitoring and evaluating new data. Until better screening tools are developed, mammograms are an important part of the fight to save women’s lives through early detection, stresses Allan.
"Mammography as a tool is pretty flawed, [but] it is the best we’ve got right now," Allan observes. "I think in 10 years, with research and looking at new technologies, we will have better ways of doing screening, which I think will hopefully reduce the amount of false-positives."
References
1. National Cancer Institute. NCI Statement on Mammography Screening. Jan. 31, 2002. Accessed at http://newscenter.cancer.gov/pressreleases/mammstatement31jan02.html.
2. Agency for Healthcare Research and Quality. Press Conference Transcript: Task Force Recommendation on Breast Cancer Screening. February 2002. Accessed at www.ahrq.gov/clinic/3rduspstf/breastcancer/transcripta.htm.
3. Olsen O, Gotzsche PC. Cochrane review on screening for breast cancer with mammography. Lancet 2001; 358: 1,340-1,342.
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