Benefits of breast X-rays are cited

New study credits mammograms with death rate decline


Addressing a major unknown in the long-standing debate over mammograms, a new study sponsored by the National Cancer Institute finds 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 percent to 65 percent of the sharp decrease in breast cancer deaths from 1990 to 2000 was because of mammograms. The rest of the decrease in deaths was because of powerful new drugs to treat breast cancer.

More than 80 percent of women ages 40 and older get mammograms now, and Dr. Russell Harris, a professor of medicine at the University of North Carolina and a member of the U.S. Preventive Services Task Force, said the new finding meant that women could feel confident the screening played a role in preventing breast cancer deaths.

That is not something 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 such as 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, Visco said, until recently the federal government paid for poor women not on Medicaid to be screened but did not pay to treat them when 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," 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 38.0 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 only explain it if both mammograms and treatment were having an effect.

"This is the first time that a study does it right in asking the effects of screening separate from therapy," said Dr. Donald Berry, the chairman of the biostatistics department at the M.D. Anderson Cancer Center. Berry is the lead author of the new paper.

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