Clinical studies show that for women of a certain age breast cancer screening really saves lives. But new research questions whether the benefits seen in those studies translate to real-world settings.
Researchers found no evidence that regular mammograms or doctor's breast exams improved breast cancer survival among average-risk women.
A possible survival benefit was seen for high-risk women, but it's unclear if this is a meaningful finding.
While the findings seem to cast doubt on the usefulness of breast cancer screening, they do not mean that women should abandon the practice, a study researcher says.
"Women should continue to be screened based on the recommendation for their age," Joann Elmore, MD, MPH, tells WebMD. "But we have to realize that screening is not perfect, and it may not have the impact on mortality that we had hoped it would."
But the director of breast cancer screening for the American Cancer Society tells WebMD there is no doubt that annual mammograms starting at age 40 save lives.
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Screening Rates Similar
Elmore and colleagues reviewed the medical records of 1,351 women between the ages of 40 and 65 who died of breast cancer between 1983 and 1998. They compared the information with data from a group of 2,501 women with no history of breast cancer of similar age and other risk factors.
The researchers reasoned that if screening really did reduce breast cancer deaths, then the women who died would have been screened less frequently than the comparison group. But that is not what they found.
Women who had regular breast cancer screening were no less likely to die from breast cancer. This held true for women at high-risk of breast cancer even though there was a suggestion of possible benefit.
When the researchers looked at breast exams performed by a doctor or mammography, neither of these screening tools alone was associated with a decrease in cancer deaths.
The findings are reported in the July 20 issue of the Journal of the National Cancer Institute.
Read Web MD's "Learn How to do a Breast Self-Exam."
Who Should Be Screened?
The American Cancer Society recommends that women get an annual mammogram starting at age 40. Robert Smith, MD, who is director of breast cancer screening for ACS, says the clinical evidence is "overwhelming" that the practice saves lives.
Smith tells WebMD that there are serious flaws in the new study, which influenced the findings. And he questions why the researchers included women screened in the early 1980s before mammography quality standards were put in place.
"I don't see how they can draw conclusions that relate to modern mammography from this study," he says. "The weight of the scientific evidence strongly supports the value of regular mammography for women 40 and older."
Cancer screening researcher Russell Harris, MD, MPH, agrees that the new study should not change clinical practice, but he says it does raise important questions about the effectiveness of breast screening.
The University of North Carolina professor of medicine called for more studies assessing the impact of mammography at the community level in an editorial published with the study.
"The message at the moment is to other researchers," he tells WebMD. "If we could say for sure that screening was having no impact, then we could stop doing it. But this is not the case."
Read Web MD"s "Learn More About Breast Cancer Screening."
Elmore says one potential explanation for a failure to show a benefit for mammography screening outside of the clinical trial setting is that the quality of screening in the real world may be inferior to that provided for women participating in studies.
And both she and Harris noted that dramatic advances in the treatment of breast cancer may have lessened the impact of screening.
"The mortality rate from breast cancer in this country has declined by 25% over the last 10 to 15 years," Harris says. "We have better drugs and we have a better understanding of how to use them, and study after study is showing that better treatments are saving lives."
The new study indicates that women at high risk for breast cancer may benefit more from cancer screening than women with an average risk for the disease. But both researchers caution that identifying high-risk women is, at present, an inexact exercise.
"We are not really good at identifying who is high risk and who is not," Harris says.
Elmore adds that she hopes her research will lead not only to more studies examining the impact of breast cancer screening at the community level but to research on better ways to identify women at high risk for the disease.
"A woman might think she is high risk if her mother had breast cancer at age 80," she says. "That may or may not be the case."
Read Web MD's "What Women Want to Know Before First Mammogram."
SOURCES: Elmore, J.G. Journal of the National Cancer Institute, July 20, 2005; vol 97: pp 1035-1043. Joann G. Elmore, MD, MPH, professor of medicine, University of Washington School of Medicine, Harborview Medical Center, Seattle. Russell Harris, MD, MPH, professor of medicine, University of North Carolina School of Medicine, Chapel Hill. WebMD Medical News: "Mammograms No Help Before Age 50."