Women in their 40s who undergo mammography screenings to detect breast cancer seldom benefit from such tests, and many may suffer emotional and physical damage from the consequences of incorrect results, according to a study by a Duke professor published today in the Journal of the National Cancer Institute.
"Screening is a lottery," said Donald Berry, the study's author and a professor at the Institute of Statistics and Decision Sciences. "The overwhelming proportion of women experience no benefit and they pay with the time involved and the risks associated with screening."
One of the reasons screening middle-aged women is difficult is that their breast tissue is often dense and screenings can mistake fat deposits for tumors.
Thus, the study concluded, many women unaffected by breast cancer have to deal unnecessarily with the emotional travails of wondering whether they have the disease. They may also undergo unnecessary treatment.
Even if a tumor is found, Berry added, it is difficult to chart the future course of the cancer.
Berry argued that women in their 40s should consider mammography carefully, but as an option rather than a necessary course of action. His analysis uncovered some evidence that mammography could be a useful procedure.
Berry looked at data from eight ongoing studies encompassing more than 200,000 women worldwide. Of the eight trials, five showed benefits from screenings and three did not.
Berry found that a regular mammogram adds about five days to the life expectancy of each woman screened. "Although some people feel passionately, no one knows for certain whether, or how much, getting mammograms before the age of 50 increases life expectancy," he said.
The study also found that when the eight trials were considered as a whole, the number of women whose deaths resulted from breast cancer was 18 percent lower among mammography subjects than among women who were not screened in their 40s. Only a small portion of either group died of breast cancer.
The National Cancer Institute does not intend to change its recommendations about mammography in light of this new study, said Dr. Barbara Rimer, director of the NCI and former director of cancer prevention at the Medical Center.
The NCI currently recommends that women between 40 and 50 receive mammograms every one to two years. After a long and controversial reevaluation in 1997, the NCI adopted the current standard.
"Both the benefits and the limitations were considered in 1997 when the recommendations were changed," said Rimer, who chaired the National Cancer Advisory Board in 1997. "Dr. Berry's kind of analysis was considered as part of that."
Berry said his study stemmed from his involvement on the NCAB, an NCI subsidiary that in 1997 neither endorsed nor recommended mammograms for women in their 40s, but concluded that women should decide for themselves.
He added that the current study was not designed to influence NCI or NCAB policy.
"It's addressed to an individual woman to decide what she should do," he said.
Of the 200,000 women in the study, Berry said that some of them probably had BRCA1 and BRCA2, the breast cancer susceptibility genes, although his study did not consider the genetic risk factors for breast cancer.
He said that he did not believe anybody has assessed the risk of screening for individuals with the susceptibility genes.
Richard Rubin contributed to this story.
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