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http://www.nytimes.com/2002/09/03/health/womenshealth/03MAMM.html

New Mammogram Studies Divided on Benefits

By GINA KOLATA

wo papers published today on the benefits and risks of mammography come to different conclusions about the breast cancer screening, continuing a debate that has erupted over the past year.

One paper, by the United States Preventive Services Task Force, makes recommendations that are generally followed by the nation's primary care doctors and concludes that the pooled data from randomized trials support mammography every one to two years for women ages 40 to 74.

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The group announced its conclusions at a news conference last winter, but its paper, being published today in The Annals of Internal Medicine, is the first formal publication of its methods, results and conclusions.

A second paper in the same issue determines that women in their 40's reap no benefit from mammography and have real risks of harm from unnecessary treatment. It presents the latest results from a study of more than 90,000 Canadian women.

Earlier findings from the same study after seven years also found no benefit, but some medical experts predicted that benefits would emerge with time. The new findings show that even 11 to 16 years after the women were enrolled, mammography had not saved any lives and had led to excess treatment.

The papers are accompanied by two editorials that call into question the widespread public assumption that the mammography debate has been settled.

It is a debate mostly taking place among researchers and some advocacy groups. Guidelines from major medical organizations are in accord that women should have regular mammograms starting in their 40's.

Dr. Steven Goodman, a biostatistician at the Johns Hopkins Kimmel Cancer Center who wrote one of the editorials, said in an interview last week that the arguments among researchers continued because the data were so inconclusive.

"If we are still unsure after looking at something like half a million women, that points to how small the risks are and how much smaller the benefit is in absolute numbers," Dr. Goodman said.

"There is statistical uncertainty around the estimates of benefits and harm, but perhaps the biggest unknown is how much harm women will find acceptable for an uncertain benefit," he added.

The current dispute on the value of routine mammograms began last year when two researchers published a paper examining the major clinical trials and concluding that nearly all were so flawed as to be invalid. Of those found acceptable, said the two scientists, Dr. Peter C. Gotzsche and Ole Olsen of the Nordic Cochrane Center in Copenhagen, the pooled data indicated that no lives were saved by mammography.

Women who had the test were just as likely to die from breast cancer as those not screened, they said in a paper in The Lancet. Moreover, the screened women had more mastectomies, more radiation therapy and more surgery. That extra treatment, in the absence of an overall benefit, made the researchers question the widespread use of mammography.

Some medical experts applauded the analysis, saying that the two investigators had pointed out serious flaws in the mammography studies and that they had appropriately emphasized that there were real risks of having the diagnostic test.

Others said that the analysis itself was flawed and that Dr. Gotzsche and Mr. Olsen had arbitrarily discarded data from major studies whose conclusions did not fit with their notion that mammography was not working.

In the meantime, the National Cancer Institute and the American Cancer Society reiterated their positions that women should start having regular mammograms at age 40 because, they said, the test saves lives. In February, Tommy G. Thompson, the secretary of health and human services, held a news conference to announce the Preventive Services Task Force's conclusion that mammography was beneficial starting at 40.

Yet the questioning continued in medical circles, with researchers publishing dueling articles, analyses and editorials in medical journals and holding debates at meetings. As the papers in the current issue of The Annals indicate, there are no signs that the dispute will soon be settled.

Dr. Steven H. Woolf, a task force member, said the message he wanted to convey in his group's analysis was that "there is clearly a mortality benefit with mammography," and he said the benefit increased as women grew older. In its paper, the group took note of what that benefit might be, and what the risks might be. It wrote that with mammography, the breast cancer death rate was reduced by about 16 percent. That meant that if 1,224 women were screened, one death might be prevented after 14 years.

Dr. Woolf said his group was also aware of the test's risks, including unnecessary biopsies and anxiety about false positive results. He added that the group also had another concern, for which, he said, the evidence was suggestive but not solid. That is the possibility that a woman will have a treatment like a mastectomy for a small and self-contained tumor that would not have been noticed in her lifetime if she had not been screened.

The group added that the clinical trials evaluating mammography had imperfections, leading it to regard the evidence as "fair" rather than "good." That complicated its determination of benefits.

"In absolute terms, the mortality benefit of mammography screening is small enough that biases in the trials could erase or create it," the group wrote in its paper. "However, we find that although these trials were flawed in design or execution, there is insufficient evidence to conclude that most were seriously flawed and biased and consequently invalid."

Dr. Woolf said the group was aware of the data from the Canadian study that failed to find benefits from screening women in their 40's, but that did not change its conclusion that mammography's benefits start at 40. The group, he explained, considered the totality of the evidence.

But Dr. Cornelia Baines of the University of Toronto, a principal investigator for the Canadian study, said she thought that the question of mammography for women in their 40's should be settled by her group's extensive data.

"After 13 years, the number of deaths was the same in the group that had mammograms and the group that had normal medical care," she said. In addition, she said, mammography was finding some cancers that would never have been detected and never have caused any problem if the women had not been screened. But once found, as would be expected and is appropriate, they were treated.

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While cancer researchers recognize that not every cancer will grow and become deadly, they cannot predict which ones are dangerous and which are not, so they treat them all.

"Some women were getting mastectomies that they didn't need," Dr. Baines said, adding that the test did not help younger women. "I think the message should be accepted by all rational people."

In an accompanying editorial, Dr. Harold Sox, editor of The Annals, wrote that his interpretation of an analysis of several large randomized clinical trials in Sweden was that they also failed to find a benefit from mammography in women under 50.

"The big picture message is that the effect of screening in any age group is limited at best," Dr. Sox said in a telephone interview. He said there appeared to be a small benefit in women starting at 50, and so he agreed with the task force for that age group. But, he said, for women in their 40's, "it is not clear that there is any benefit at all." With such questions, he added, "I think we should be worried about harms."

In interviews, medical experts with different views on the test's value maintained opinions that they had previously expressed.

Dr. Harmon Eyre, chief medical officer of the American Cancer Society, applauded the task force's report. "It confirms the value of mammography both in women over age 50 and under age 50," he said. "That in my mind is the message."

Dr. Larry Norton, past president of the American Society of Clinical Oncology, said he, too, advocated screening, starting at 40. "On the basis of the total amount of information available," he said, his conclusion is to "continue to screen."

But Dr. Donald Berry, chairman of the department of biostatistics at M. D. Anderson Cancer Center in Houston, said, "If there is a benefit, it is not very great." Dr. Berry is a member of an expert group, the P.D.Q. screening and prevention editorial board, which writes information for the National Cancer Institute's online database. It concluded in January that evidence was insufficient to show that mammograms prevented breast cancer deaths.

Dr. Goodman said that despite the figures disseminated, like the task force's finding that there was a 16 percent mortality benefit with mammography, uncertainty reigned, and most scientists who studied the data were well aware of it. "That's the shadow element. There is a level of scientific uncertainty that is not reflected in the numbers but exists in the minds of all the analysts," he said.

In the end, he said, the mammogram debate reflected a conundrum of modern medicine. The answers that are needed — what are the benefits and what are the risks — are right at the fuzzy boundary of what science can deliver. He said it was like looking through a microscope at something just at the limits of resolution. "Reasonable people can differ on what the evidence is," he said.

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