Headlines
As reported by The New York Times, October 27, 2005.
Mammograms Validated as Key in Cancer Fight
By Gina Kolata
Addressing a major unknown in the longstanding debate over mammograms, a new study sponsored by the National Cancer Institute found that the screening test contributed to a pronounced drop in the death rate from breast cancer.
The study, being published today in The New England Journal of Medicine, concludes that 28 to 65 percent of the sharp decrease in breast cancer deaths from 1990 to 2000 was due to mammograms. The rest was attributed to powerful new drugs to treat breast cancer.
More than 80 percent of women 40 and over get mammograms now, and Dr. Russell Harris, a professor of medicine at the University of North Carolina and a member of the United States Preventive Services Task Force, which issues medical practice guidelines, said the new finding meant that women could feel confident the screening played a role in preventing breast cancer deaths.
That is not something Dr. Harris would have said before the study was published.
He and others cautioned that before deciding to be screened women should weigh the risks of mammograms, like false positives and being treated for tumors that would not have spread if they were left alone.
The study was an effort to understand why the breast cancer death rate had dropped so drastically so rapidly - 24 percent from 1990 to 2000. Was it mammograms, which can find cancers early when they may be more treatable, or was it powerful new drugs to treat the cancers?
The two factors had been tested in clinical trials, but researchers did not know what occurred in the real world, where women did not always follow medical advice and doctors did not always use the tests and drugs as carefully as in the studies.
Most of the researchers expected that drugs would be working, because the clinical trials were so persuasive. But there was a sharp dispute over whether mammograms, whose clinical trials were more ambiguous, had much benefit outside those trials.
The debate over the effectiveness of mammograms has been bitter, drawing in cancer researchers and advocates and involving questions about spending and whether opportunities to save lives were being squandered. Some experts said that mammograms were unlikely to be very effective and that it was a waste of money and resources to have every woman 40 and older have one a year.
Other experts said that mammograms were crucial and that without screening to find cancer early, the treatments would not be nearly so effective.
"The emphasis was always on mammograms, mammograms, mammograms," while treatment was given short shrift, said Fran Visco, director of the National Breast Cancer Coalition, an advocacy group.
In fact, Ms. Visco said, until recently the federal government paid for poor women not on Medicaid to be screened but did not pay to treat them if cancer was found.
Other experts like the American Cancer Society insisted that annual mammograms were essential. Dr. Carolyn D. Runowicz , a gynecologic oncologist at the University of Connecticut and the incoming president of the society, said the death rate would not have fallen without the increase in mammograms. The decline in deaths "is due to better screening, better use of screening," Dr. Runowicz said.
For the new study, the National Cancer Institute asked seven research teams to explain what had occurred. The death rate was nearly flat from 1975 until 1990, when it was 49.7 per 100,000 women ages 40 to 75. In 2000, the rate dropped, to 38 per 100,000 for that age group.
In the meantime, mammography for women older than 40 soared. In 1985, about 20 percent of women were estimated to have had mammograms in the prior two years. In 2000, the figure was 70 percent.
At the same time, chemotherapy and hormonal therapy with tamoxifen, which blocks the effects of estrogen that can fuel breast cancer, had come on the scene, and their use had spread rapidly.
To develop their estimates, the researchers built computer models of the disease, its detection and its treatment, asking whether they could explain the falling death rate from 1990 to 2000. The answer, they all agreed, was that they could explain it only if both mammograms and treatment were having an effect.
The debate over mammograms began in the 80's, when the National Cancer Institute questioned their benefits for women in their 40's. In 2002, the British journal Lancet published a paper saying the benefits of mammograms for women of any age were unclear.
One group, the P.D.Q., an independent group that analyzes data for the National Cancer Institute to present to the public, said it could no longer tell women that mammograms prevented breast cancer deaths.
That group, of which Dr. Harris is a member, said the clinical trials of mammograms had not made a strong case that lives were saved. Just because a cancer is found early, the group added, does not mean that the patient is necessarily better off. Some cancers are curable, no matter when they are found. Others are incurable, no matter when they are found.
To know that a screening test works, experts need strong evidence from clinical trials, and the evidence from the mammography trials was just not convincing to them.
In response, health organizations, including the American Cancer Society, the American Society of Clinical Oncology and the American Academy of Family Physicians, took out advertisements saying that mammograms saved lives and that they were concerned that the debate was going to erode women's confidence in the test.
In subsequent years, Dr. Harris said, he and others became convinced that mammography could work, in ideal clinical trial settings in studies in Sweden. But he wondered what its effects were in the United States today.
"The question was not whether you could make mammography work under ideal circumstances," Dr. Harris said, "but does it work now, in the real world right now?"
It was a question of particular importance, he said, because treatment was much better than it had been even a decade before and improving day by day. That led him and others to ask whether mammography was making much of a difference in reducing the death toll.
Among the skeptics was Dr. Donald Berry, the chairman of the biostatistics department at the M. D. Anderson Cancer Center and a member of the P.D.Q. panel. Dr. Berry led one of the seven teams of statisticians whose paper is published today and is the lead author of the new paper.
"This is the first time that a study does it right in asking the effects of screening separate from therapy," Dr. Berry said. "My own view has changed a little because of the solidifying of the benefits."
He and others emphasized, however, that mammograms had risks and that women should be counseled before deciding to be screened.
The risks include false positives; 90 percent of what looks like cancer turns out not to be. They also include the problem that a proportion of cancers - from the clinical trial data, Dr. Berry estimates at least at 30 percent - that are detected and treated would not have caused a problem if they had been left alone. Those are the indolent cancers, ones that never grow much or spread outside the breast. But because no one knows which cancers are dangerous and which are not, doctors treat them all.
Nonetheless, Dr. Berry said, when the P.D.Q. last discussed mammography, in 2002, the concern was that the risks were clear but that the benefits uncertain.
"This makes the benefits more certain," he said.