Ten years ago, the federally sponsored Institute of Medicine published a report summing up the pluses and minuses of breast cancer screening. It begins,
“The public has a seemingly insatiable appetite for news about breast cancer, [a] disease that women most fear. The mass media, both news and advertising, is the main source of health information for many Americans. Unfortunately, there is considerable evidence that the media portrays breast cancer unrealistically, and that women’s perceptions of their risk of having breast cancer and dying from it—and, not coincidentally, of the benefits of various tests and treatments for breast cancer, including mammography—are similarly skewed.”
Reporters have long channeled the interests of organizations with a stake in promoting mammography. With American women receiving 40 million mammograms a year at a cost of $3 billion, screening is big business.
But according to the preponderance of clinical trials, mammographic screening seriously harms millions of women while salvaging perhaps one life per 1,000 women screened.
The fact that screening causes considerable harm to healthy women is difficult for many people to believe, since early detection makes intuitive sense.
Researchers at the Max Planck Institute in Berlin summed up why women vastly overestimate the benefits of screening: the presentation of risk in relative instead of absolute terms.
My middle-aged spouse recently received a flyer from Kaiser Permanente announcing that “one out of eight women will develop breast cancer in their lifetime.” It did not mention that the chance of her being diagnosed this year is 3/10 of 1 percent, or that her current risk of dying from breast cancer is a tiny fraction of that small percentage.
The one-in-eight figure refers to risk at birth, which diminishes with age. As explained in part two of this series, it does not mean that one in every eight women will get breast cancer. Far from it.
Kaiser urged my beloved to get regular chest X-rays for “peace of mind,” and a doctor signed off, “As your health care champion, I would like you to have a mammogram as soon as possible. Screening saves lives and keeps families together.”
But does it?
The takeaway
The only way to assess whether mammographic screening reduces deaths is through decades-long clinical trials that follow women across their lifetimes.
Several major trials were conducted in the United States, Canada and Europe. The expensive, logistically complex studies enrolled hundreds of thousands of women and randomly assigned them to either a group that would be regularly screened or an unscreened group.
Both groups were tracked to see how many women in each group died from breast cancer—which is no easy task, since people move and change names. Death records are notoriously unreliable sources of epidemiological information; as people age, they are often afflicted with multiple maladies, making it difficult to extract a single cause of death from the range of co-morbidities.
In 1997, a New York-based study that commenced 34 years earlier proclaimed a 25 percent lower breast cancer mortality rate for screened women. But the effect was overstated as a relative ratio; there were 416 breast cancer deaths among the 62,000 middle-aged women studied. The screened group suffered 56 fewer mortalities than the unscreened group.
The New York study was criticized for harboring a bias in favor of screening, caused by the imperfect randomization of women when they were assigned to their cohorts. There were also problems with the technical quality of the screening itself, and with tracking causes of death in the large cohorts.
But as one of the few large trials to support the efficacy of mammography, it is widely cited as evidence that X-ray screening works.
A Swedish study that started in 1977 eventually reported twice as many deaths in a non-screened group as in a screened group—an unprecedented benefit of mammography, if true.
But it, too, was criticized, both for the difficulty in tracking cause of death and for having enrolled too many women with pre-existing breast cancers.
In February 2014, the British Medical Journal published the final results of the Canadian National Breast Cancer Screening Study. With the exception of a few professional organizations of mammographers, the scientific community considers the trial rigorously designed and implemented.
The trial commenced in 1980 under the supervision of researchers at the University of Toronto and several hospitals, and enrolled 89,000 women. For a quarter of a century, researchers followed the medical histories of participants, who had been randomly assigned to either a group that received annual mammograms for five years or a group that received no mammograms during that time.
Like the other studies, the goal was to discover if the members of one group died more frequently of breast cancer.
This study found that members of both groups died of invasive breast cancer at the same rate, meaning that screening did not reduce deaths. In addition, it found that 22 percent of the invasive cancers diagnosed by mammography were overdiagnosed and overtreated with surgery, chemotherapy and radiation.
In other words, one of out five screened women was incorrectly diagnosed with a malignant carcinoma.
The New York Times headlined the findings of the Canadian trial as “casting doubt on the value of mammography.” The normally staid editorial board of the 170-year-old British Medical Journal published an editorial titled, “Too much mammography: Long term follow-up does not support screening women under 60.”
The journal subsequently published a series of papers critical of screening healthy women, and proclaimed that women are grievously harmed by the overtreatment of “pre-cancers” and non-threatening early breast cancers.
But the Canadian study elicited howls of outrage from organizations that have long advocated for mammographic screening, such as the American College of Radiology and the Society of Breast Imaging. Memorial Sloan Kettering Cancer Center claimed that women are not really concerned about “the various side effects of screening,” and, harkening back to the problematic New York study, stated that annual mammograms “decrease the likelihood that women will die of breast cancer by at least 25 to 30 percent.”
But the Canadian study is not a historical outlier.
In 1993, the National Institutes of Health declined to recommend mammography for women in their 40s, asserting that clinical trials had shown no reduction in mortality due to screening.
A trial on the effects of mass screening in Norway, as reported in the New England Journal of Medicine in 2010, found that although screening was associated with a possible reduction in mortality, “To save one life, 2,500 women would have to undergo mammographic screening regularly for over a decade,” with all of the attendant harms from false positives and overdiagnoses.
In 2013, the Copenhagen-based Cochrane Breast Cancer Group published a metastudy assessing the scientific validity of the existing major clinical trials on the efficacy of mammography. In total, these trials had followed 600,000 women during the last half-century.
The Danish collaborative concluded that there is no hard evidence that screening reduces deaths from breast cancer, but that “for every 2000 women invited for screening throughout 10 years, one will avoid dying of breast cancer and 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily.” (Being invited for screening does not mean that the screening took place, but that way of framing the data can measure the overall impact of screening programs.)
Furthermore, the Danish study reported, more than 200 of those 2,000 invited women “will experience important psychological distress including anxiety and uncertainty for years because of false positive findings.”
The scientists noted that because conventional cancer treatments have improved since the trails commenced, the mortality benefit from mammographic screening might actually be zero.
In April 2014, based on the Canadian and Danish findings, the Swiss Medical Board recommended abolishing mammography.
The board noted that for every breast cancer death prevented in American women over a 10-year course of annual screening beginning at age 50, “490 to 670 women are likely to have a false positive mammogram with repeat examination; 70 to 100, an unnecessary biopsy, and 3 to 14 an overdiagnosed breast cancer that would never have become clinically apparent.”
The takeaway is that major clinical trials show that screening may reduce the number of women who die from breast cancer from five to four in 1,000—that is, by one life saved in 1,000 women screened.
But that fractional difference has been promoted by screening advocates as a 20 percent relative risk reduction, leading many to believe that screening saves 200 out of 1,000 women screened.
Here is the rub: if you are that woman in a thousand whose life is saved by early detection, you want to get screened. But would you put the future of population screening up to a vote by the women who will be harmed?
Let’s look at the big picture. If mammography saves the life of one woman per thousand screened, and 40 million women get annual mammograms for 10 years, then 4,000 women escape death. But that benefit is theoretically offset by 20 million false positives, 4 million unnecessary biopsies and half a million unnecessary treatments.
Digital mammography, which delivers less radiation per dose than traditional film screening, is predicted to induce 86 cancers—11 of which are fatal—per 100,000 women screened over their lifetimes, according to a 2010 study by the Radiological Society of North America.
That sounds like small damage, perhaps. But if 40 million women were to receive digital mammograms, they could eventually be afflicted by 34,400 radiation-induced cancers and 4,400 fatalities, not to mention overtreatment.
Science overridden
The body of research examining the efficacy of screening mammography is clearly legion. Panels of volunteer experts at the Institute of Medicine and the United States Preventative Services Task Force have periodically summed up the lessons to be learned.
“Saving Women’s Lives,” the Institute of Medicine’s 2005 analysis of mammographic screening, flew under the radar of national media. It noted that not all radiologists and pathologists are equally experienced or talented, and that harmful diagnostic errors could be offset by patients demanding second and third opinions.
The report noted that the fear of malpractice lawsuits drives much of the overdiagnosis that subjects millions of women to unnecessary medical procedures.
It also noted that uninsured women are 50 percent more likely to die from breast cancer than are women with private insurance. At the time, the breast cancer mortality rate for black women was 35 percent higher than for white women—whose incidence rate was nevertheless higher due to more screening.
In 2009, the U.S. Preventative Services Task Force recommended that women wait until age 50 to start getting mammograms unless they have a family history of breast cancer.
The Congressionally funded task force based its recommendation on two studies it had commissioned, which concurred with a wealth of others showing that the high rate of mammographic false positives wipes out any social benefit from screening women under 50.
The task force advised women over age 50 to proceed with caution in deciding whether to get regular mammograms, and to assess their own “values regarding specific benefits and harms.”
It was a scientifically uncontroversial suggestion that was nevertheless framed as controversial by media outlets echoing the outrage of organizations that sell mammograms.
Politics trumped science when Health and Human Services Secretary Kathleen Sibelius rejected the task force’s recommendation, advising women under 50 to get annual breast X-rays anyway. She did not present any evidence as to why.
It was not the first time a medically conservative panel was overridden by the might of Big Pink, the media-savvy business complex of medical-device manufacturers, pharmaceutical and chemical companies, radiology groups and politically powerful corporatized funders such as the Susan Komen Foundation, the American Cancer Society and the Avon Foundation for Women.
The domination of the breast cancer awareness message by industrial interests has serious medical consequences. Fear-driven women are increasingly opting for single and double mastectomies, sometimes only on the basis of a genetic profile.
Surgical treatment for early breast cancer is expanding in the United States, according to a 2015 study published in the British Medical Journal. More women are choosing mastectomy over breast-conserving surgery, with the greatest increase among women diagnosed with ductile carcinoma in situ, or D.C.I.S.
Twenty percent of women diagnosed with early breast cancer consider getting a double mastectomy, and 7 percent choose to.
In the United Kingdom, the journal reported, 99 percent of women with screen-detected breast cancer undergo surgery and two thirds have adjuvant radiotherapy and hormone therapy. About 20 percent of these are “undergoing cancer treatments to ‘cure’ a disease which they would never have had without screening.”
According to a series of studies published in other journals, women with higher incomes and educations are increasingly opting for single and double mastectomies.
It is relatively easy to debunk the theme that wealthy white women are more at risk of breast cancer. Solving the moral problems posed by mammography, however, is beyond the pay grade of most epidemiologists, not to mention journalists.
Despite the best intentions and designs, the decades-long clinical trials on the efficacy of mammography are guaranteed to be skewed to some extent by hidden biases and “confounding” effects. This makes it extremely difficult to say with certainty that the trials precisely reflect what goes on in the more chaotic world.
Still, after accounting for overdiagnosis and improved treatments, studies show that the breast cancer mortality rate has remained basically flat since the advent of mammography, despite increasing incidence rates, indicating that screening has not impacted the death rate—even though it has saved or prolonged some lives.
Otis Webb Brawley is the chief medical and scientific officer of the American Cancer Society. In his 2011 book, “How We Do Harm,” he wrote, “Screening can lead to unnecessary treatment that can have its own terrible side effects … whereas the health benefit of screening is only theoretically possible.”
On the other hand, he continued, “The financial benefits of screening for a long chain of medical businesses have been measured almost to the penny. This is a game with a predetermined outcome: everyone but the patient wins.”
A marketing man at a major American cancer center explained how the real world works to Dr. Brawley: “We make up the cost of offering free screening by charging for evaluation of the abnormal screens. [Some] will have cancer. We hit bingo with them.”
Caveat emptor.
Tune in next week for a deep dive into the troubled science and politics of the Avon-funded, and now defunct, Marin Women’s Study.
Read part one here: https://www.ptreyeslight.com/article/busted-breast-cancer-money-and-media-part-one-renee-willards-story
Read part two here: https://www.ptreyeslight.com/article/busted-breast-cancer-money-and-media-part-two-climbing-risk-mountain
Read part three here: https://www.ptreyeslight.com/article/busted-breast-cancer-money-and-media-part-three-marin-syndrome
Read part four here: https://www.ptreyeslight.com/article/busted-breast-cancer-money-and-media-part-four-canary-gold-mine
Read part five here: https://www.ptreyeslight.com/article/busted-breast-cancer-money-and-media-part-five-does-hormone-replacement-therapy-cause-breast
Read part seven here: https://www.ptreyeslight.com/article/busted-breast-cancer-money-and-media-part-seven-life-and-death-marin-womens-study
Read part eight here: https://www.ptreyeslight.com/article/busted-breast-cancer-money-and-media-part-eight-how-zero-breast-cancer-pays-its-bills
Read part nine here: https://www.ptreyeslight.com/article/busted-breast-cancer-money-and-media-part-9a-bad-data-dirty-laundry
Read part ten here: https://www.ptreyeslight.com/article/busted-breast-cancer-money-and-media-part-ten-bad-data-audit-trail
Read part eleven here: https://www.ptreyeslight.com/article/busted-breast-cancer-money-and-media-part-eleven-story-abigail-adams-how-california-cancer