New Book: Mammography Screening—truth, lies and controversy
Posted by medconsumers on March 31, 2012
What happens when a popular cancer screening technology is found to be far more harmful than lifesaving? When the finding becomes clear decades after it was oversold to the public? When a lucrative industry, in terms of equipment, breast biopsies, drugs, etc., has already built around it that is now impossible to dismantle?
One might hope that science would win out. After all, mammography has the distinction of being a cancer screening test with extensive research behind it. In his new book Mammography Screening: Truth, Lies and Controversy (Radcliffe Publishing, London/New York: 2012), physician and research scientist, Peter C. Gøtzsche recounts what it was like to take a hard look at that research and find it didn’t match up with mammography’s sterling reputation.
The near-universal reaction? Shoot the messenger. Vicious attacks came from researchers, policymakers, and physicians. Too often aimed at the man himself rather than his critique. Opinions were fixed—mammography is risk-free and lifesaving. Anyone who disagrees publicly is causing deaths in women who might reconsider and stop having mammograms. The book describes the scientist’s 11-year investigation that uncovered mammography’s considerable harms, though they were “hiding” in plain sight—in the original studies that had long ago established mammography screening as a lifesaver.
Dr. Gøtzsche, director of The Nordic Cochrane Centre, Copenhagen, describes himself as someone who knew little about mammography when, in 1999, he was asked by the Danish Research Council to do an in-depth assessment of all mammography-related research. A statistician and expert in clinical trial design and analysis, Dr. Gøtzsche was the right man for the job. Denmark was considering a national screening program, but first wanted to know more. Bad signs were already showing up in Norway where such a program was underway. Screening decreased breast cancer deaths but, ominously, it hadn’t decreased the rate of deaths from all causes. Even more alarming, mammography failed to detect the most aggressive, deadly form of breast cancer.
Central to Dr. Gøtzsche’s conclusions are the nine randomized clinical trials that included a half million women altogether. The first took place in New York City, in the early 1960s; the last two trials were conducted in Canada and Sweden in the 1980s. “We were baffled by what we found,” he wrote. “We had expected them to be more convincing considering how popular mammography screening had become, despite its high cost.”
The results of these nine trials focused narrowly on mammography screening’s role in reducing breast cancer deaths. Dr. Gøtzsche may well be the first to step back and look at the big research picture, assessing the total death rate and the harm to women. His assessment for the Danish National Board of Health described the benefits as uncertain and raised the possibility that screening could cause more harm than good. It was ignored.
Dr. Gøtzsche continued mining the data from the nine trials and publishing frequently over the next decade. The first paper, co-authored with statistician Ole Olsen, appeared in 2000 in the British journal, The Lancet. But it was their second paper for The Lancet in 2001 that set off a furious international reaction. The nine mammography trials emphasize the number of breast cancer deaths among the participants, but Olsen and Gøtzsche contend that deaths from other causes must also be taken into consideration. These trials show that many more women given regular mammograms are treated for breast cancer than the unscreened women, and these treatments themselves may cause fatalities. Furthermore, overtreatment of ductal carcinoma in situ, often with mastectomy, was identified as “a considerable risk of mammography screening because most cases do not become invasive.” (Disclosure: I serve on The Nordic Cochrane Centre’s advisory board, am quoted in this book, and have reported Dr. Gøtzsche’s work ever since I first came across it in 2000.)
Reactions in the U.S. media were exceptionally virulent and prolonged. It was likely the first time that most physicians as well as the general public heard that some cancers will never cause death or symptoms. But this was not the first high-decibel mammography media controversy. In 1992, when the Canadian trial was published, it was roundly trashed because it came up with an unpopular finding: Mammography screening did not reduce breast cancer deaths, though it increased the number of cancers detected. Dr. Cornelia Baines, co-director of this trial, expected fellow scientists to take a dispassionate look at the finding to see why it differed from that of the earlier trials. Instead, she became the target of numerous attempts to silence and discredit her.
When the mammography controversy surfaced again in the media in 2001, it was the policymakers, the radiologists, and the breast cancer specialists who came down hardest on Olsen and Gotzsche. To accept their conclusions would mean that hundreds of thousands of women worldwide have been treated for a type of breast cancer that would either regress or remain dormant. Who would “dig deep” into that possibility? Certainly not the doctors who for years have been sending their patients for mammograms. And certainly not the radiologists whose income had increased mightily—less from the screening test itself than from the money-making ancillary activities like stereotactic needle biopsies, continuing education courses, magnetic resonance imaging, and biopsy-related patents (click here for one example).
Most women don’t want to hear about mammography’s harms either. Fear of breast cancer sold them on mammography in the first place—without it, there would be no action to take. In the early 1970s when mammography screening was first introduced in the U.S., most American women were not particularly fearful of breast cancer, largely because it was seen as an old woman’s disease. But a multi-national cancer drug maker took care of that “problem” with annual breast cancer awareness campaigns featuring young breast cancer victims. The fear level is kept high for doctors, too, who are frequently reminded that “failure to diagnose breast cancer” is a leading cause of malpractice lawsuits.
Cancer charities take a well-deserved hit in this book for their refusal to admit that screening has a downside. Their misuse of statistics seems calculated to inflate the benefit of cancer screening. Consider the 30% reduction in deaths bandied about in the early years of mammography promotion. This statistic was downgraded recently to 15% by the U.S. Preventive Services Task Force. But both of these are relative risk statistics, which are typically misunderstood by doctors and consumers alike. Most relevant is the absolute effect of screening, not the relative effect, points out Gøtzsche who provides this explanation: “If 2,000 women are screened regularly for 10 years, 1 woman will avoid dying from breast cancer, and 10 healthy women who would not have been diagnosed without screening, will have breast cancer diagnosed and be treated unnecessarily.”
At the end of last year, the Canadian Medical Association Journal invited Dr. Gøtzsche to write an editorial entitled, “Time to stop mammography screening?” The Canandian Task Force on Preventive Health Care had just issued new guidelines, stating that “women who do not place a high value on a small reduction in breast cancer mortality, and who are concerned with false-positive results on mammography and overdiagnosis, may decline screening. ” Dr. Gøtzsche describes this as “an important step in the right direction, away from the prevailing attitude that a woman who does not undergo screening is irresponsible.”
It’s hard to imagine that this could ever happen here in the U.S.
This book can serve as a guide to physicians and women who want to make their own informed decisions about mammograpy screening, who want an honest in-depth assessment of the research—one that should have given to the public before the introduction of mass screening. A similar “promote the test first, learn the harms later” story has unfolded recently about the PSA screening test for prostate cancer. You just might want to sharpen your critical skills and prepare in advance for the next cancer screening disaster.
Maryann Napoli, Center for Medical Consumers©
More about Dr. Gotzsche’s work:
Free mammography screening leaflet from the Nordic Cochrane Centre It is also available at The Nordic Cochrane Centre website in 13 languages.
Cut your risk of breast cancer—avoid screening mammograms. One-third of all breast cancers found on a mammogram are the forms of breast cancer that would never cause death or symptoms.
Breast cancer death rate has dropped, but not due to mammography Improvements in breast cancer treatments are most likely cause. ‘Before and after’ studies conducted in countries that introduced mammography in the 1990s verify what was noticed in Norway in this era: Screening does not detect the most deadly form of breast cancer; it has not reduced the occurrence of advanced cancers.
Poster for the 2002 Cochrane Colloquium U.S. media coverage of the 2001 Lancet paper.