For the better part of a century, it would have been unthinkable to treat primary breast cancer with anything but the operation pioneered in the 1890s by William Halsted, M.D., one of the most prominent surgeons of his day. Beginning in the 1970s, the Halsted era drew gradually to a close when randomized controlled trials found that the operationgenerally known as radical mastectomywas no more effective than less drastic surgery (sometimes in combination with radiation). Could a similar fate await the current gold-standard status of screening mammography? Will a time come when its popularity dwindles, too?
Barron Lerner, M.D., Ph.D., associate professor of medicine and public health at Columbia University in New York City, does not see it happening soon. But as the author of The Breast Cancer Wars, a book to be published by Oxford University Press next year, he noted that, while screening mammography is hardly new a new technology, there is considerable disagreement about its utility.
|
One thing undisputed about mammography is that it can pick up smaller cancers than either breast self-examination or clinical breast examination. Paradoxically, however, there are tumorsand they are fairly commonthat hands find and mammograms miss. The key question, therefore, is whether early detection, by whatever means, translates into fewer cancer deaths. In other words, does advancing the date of diagnosis and thus the onset of therapy actually save lives?
The first randomized controlled trial to take a hard look at the matter is popularly known as the HIP study and was launched by the Health Insurance Plan of Greater New York in 1963. In it, some 61,000 women, 4064 years old, were screened once with mammography and clinical breast examination and for the next 3 years were either rescreened with these methods or not screened at all so that they served as controls. Although many now think of the 1960s as ancient history, the HIP study had an impact that has by no means disappeared.
As there was a statistically significantly smaller number of breast cancer deaths among the screenees as time went on than among the controls, the HIP study established the principle that it was better to screen than not. And when the same was true in five subsequent randomized controlled trialsfour in Sweden and one in Scotlandthe idea that breast cancer screening is useful was confirmed. Still, ambiguities lurked beneath the surface of these trials that were to make straightforward answers to some simple questions elusive.
Surely the most vexing of such questions is whether the screening should be universally recommended to women in their 40s. The problem, in brief, is that the HIP and its fellow trials enrolled too few women in the 4049 age group to provide an answer that had sufficient statistical power to be definitive. That, in turn, made two interpretations of the data possible.
One suggested that periodic screening of "forty-somethings" should get the benefit of the doubt and be universally recommended; the other, that it would make more sense to start universal screening at 50 because the risk of the disease before thatwhile it grows during the 40sis, nonetheless, very low. In the HIP trial and the five others, for example, most of the 4049-year-old women screened who subsequently developed breast cancer were at least 50 at the time of diagnosis. Moreover, their likelihood of false-positive mammograms is greater than for older women.
Anthony Miller, M.D., and a colleague, Cornelia Baines, M.D., took the age issue by the horns in organizing a multicenter study to follow more than 50,000 Canadian women who were 4049 years old in the years 1980 to 1985. (Both investigators were then at the University of Toronto, where Baines still is. Miller, now emeritus there, is in Germany at Heidelberg University.) For 4 or 5 years, depending on their date of entry into the study, half these women had a clinical breast examination and mammography; the resti.e. the controlshad only a single hands-on breast examination. This was (and remains) the only trial designed to directly test the efficacy of breast cancer screening in women who began screening in their 40s.
|
|
Ultimately the accusations became so shrill and relentless that the National Cancer Institute of Canadathe projects sponsorordered an investigation and chose two U.S. physicians to do itJohn Bailar, M.D., of the University of Chicago, and Brian McMahon, M.D., of Harvard University. Bailar recently recalled that they found evidence of "some slippage" in the conduct of the trial, but not, he said, of "a sufficient magnitude" to have invalidated the results.
Still, neither the Bailar-McMahon report (which was published in 1997) nor anything else mollified the critics of the Canadian trial. An international workshop held in Bethesda, Md., in 1993 was a prime example of the sort of thing that aroused the critics ire. It reached the conclusionfrom a meta-analysis of all the data then availablethat routine mammograms for women, starting at 50, reduced breast cancer mortality by as much as 39%, but that routine mammography in younger women was of no proven benefit.
The critics were, if anything, even more displeased with what transpired at a consensus conference the National Institutes of Health convened on its Bethesda campus in 1997. At that conference, the panel charged with weighing the pros and cons of screening mammography for women in their 40s advised them to decide the matter for themselves because, it said, rigorous scientific justification for a definitive recommendation was lacking. After the consequent heat and furor in the press and in Congress, the National Cancer Institute followed its advisory boards advice and took its present position that "women 40 and over" should have screening mammograms every 1 or 2 years.
The tempers and the rhetoric of the critics have cooled somewhat since then. However, with this Journals Sept. 20 publication of the 13-year follow-up results of the Canadian study, they flared again.
The new report focuses on breast cancer death rates in nearly 40,000 Canadian women who were 5059 years old in 1980 to 1985 and were annually screened in the 1980s with mammography plus meticulous 10-minute clinical breast examinations by health professionals or the thorough clinical breast examinations alone. The results, in a nutshell, were that in the 13 years after the study had started the addition of mammography to the hands-on examination had not reduced breast cancer mortality.
That is not, of course, a message that gladdens the hearts of mammographers, and the American Cancer Societytraditionally a strong enthusiast for their technologyimmediately weighed in with a press release calling the study "controversial" and casting doubt on how it was conducted and thus on its credibility. The American College of Radiology and the Canadian Association of Radiologists both dismissed the results of the trial, saying the trial was "badly flawed." One mammographer was quoted as saying that publication of the study by the Journal was "unconscionable." There are, however, those who think that the groups disparagement of the study is no reason to dismiss it outright.
One of these is surgeon Susan Love, M.D., founder of her own nonprofit breast cancer foundation. What interests her about the study is that its having teased apart the effects of screening mammography and clinical breast examinations raises the possibility that certain kinds of breast tumors may be better found by one method and others by another so that it could be of practical importance to test this hypothesis with further research.
Suzanne Fletcher, M.D., of Harvard Medical School, also thinks the Canadian study has value. For one thing, she said, it is the first study to have ever asked whether adding mammographynow a $4 billion a year industry in the United States aloneto careful physical breast examination actually makes sense and if so, under what circumstances. And for another, the clinical examinations the study employed were more "thorough and systematized" than is usual at least in the United States. In her view, that in itself suggests that "we should, perhaps be better training clinicians in physical examination of the breasts."
She noted that while mammography in the Canadian study found breast cancers when they were smaller and apparently in an earlier stage than did the physical examinations it did not ultimately decrease the breast cancer death rate. Thats "tough for people to understand," she admitted. "But as we have come to understand that cancer is less an either/or phenomenon than an accumulation of abnormalities, its a limitation that cancer screening studies (for many types of cancer) are bumping into more and more frequently."
Nor, she believes, will technical advances necessarily change the situation for the better. Again using mammography as an example, she noted that it has had the benefit of many technical advances over the years and that more of theme.g., digital mammographyare on the way. Yet, as she put it, "the amount of protection mammography screening confers [on women] has looked remarkably similar" since the technology was in its infancy decades ago.
Absent unforeseen developments, it is probably safe to predict that mammography for screening will continue to be as much about strongly held opinions and political pressures as about science.
This article has been cited by other articles in HighWire Press-hosted journals:
![]() |
||||
|
Oxford University Press Privacy Policy and Legal Statement |