Mammography’s days numbered

DRUG BUST by Alan Cassels

• The people’s briefing note on prescription drugs
Portrait of columnist Alan Cassels

• The headline that landed like a drone strike on the medical world asked one simple question: “Time to stop mammography screening?” The editorial by Dr. Peter Gotzsche, a Danish physician and one of the world’s experts on the science behind breast cancer screening, was published in the Canadian Medical Association Journal in November of 2011. Gotzsche’s article summarized the science to date and made the strongest argument yet against the alleged values of mammography. The conclusion: “If screening does not reduce the occurrence of advanced cancers, it does not work.”

From scouring the evidence from trials involving thousands of women over many years, you would think there would be substantial evidence showing that women who are screened, versus those not screened, would have a substantially reduced risk of dying from breast cancer. Problem is, that’s not at all what the science says. In fact, the opposite is more likely true. Gotzsche follows this to the logical conclusion with a very provocative line: “The most effective method we have to reduce the occurrence of breast cancer is to stop screening.”

Let’s give this some context: if what Dr. Gotzsche said is true, the multi-billions of dollars spent around the world every year to try to detect and prevent breast cancer from killing women is likely wasted. Not only could these huge screening programs be a total waste of health budgets, they could be making it worse for women by not providing effective kinds of protection. The fact that his article appeared in a Canadian medical journal might subtly suggest that perhaps Canada should be the world’s first country to put the brakes on breast cancer screening; some of the best research on screening mammography has been done right here in this country.

Well, I’m here to say Canada didn’t win that prize. But more on that later.

There is no doubt the subject is highly controversial – and explosive. With the fate of mammography screening at stake and independent scientists like Peter Gotzsche and others finding very troubling truths, you can imagine the counter-reaction is volatile and well-funded. After all, in the US alone, nearly $8 billion a year is spent on carrying out the mammograms, doing biopsies and surgeries, delivering chemotherapy and drugs as well as providing the salaries of the radiologists, nurses and physicians, it all adds up. Ultimately, many people derive their income from keeping mammography programs alive. This ship is not likely to alter course quickly as old beliefs die very hard, even as one wise man said, “when demonstrably false.”

But how false is it? To get the ‘long view’ on breast cancer screening, a recent study published in February of this year in the British Medical Journal quantified the unnecessary harm caused by mammography screening. Canadian researchers Anthony Miller and Cornelia Baines at the Dalla Lana Faculty of Public Health in Toronto were early pioneers of breast cancer screening research in Canada and began studying it in 1980. Their study, the Canadian National Breast Screening Study, continued to assess the effects of breast cancer screening after 25 years of follow-up and found that “Annual mammography in women aged 40-59 does not reduce mortality from breast cancer beyond that of physical examination or usual care when adjuvant therapy for breast cancer is freely available.”

It’s not that it doesn’t “work” in reducing breast cancer deaths, but that they were able to quantify the level of overdiagnosis. They write, “Overall, 22% (106/484) of screen- detected, invasive breast cancers were overdiagnosed, representing one overdiagnosed breast cancer for every 424 women who received mammography screening in the trial.” Among the harms to these women are many false positives, unnecessary biopsies or overdiagnosed breast cancer that would never have gone on to hurt the woman. With over 60 online ‘comments’ published following that article, it’s one of the most insightful sets of ‘back and forth’ discussions on breast cancer screening you will ever read.

“Yes, but my life might have been saved,” breast cancer survivors will say, refusing to believe that mammograms are now considered useless. Gotzsche said the world has turned the corner on mammography screening programs for two main reasons: very effective therapies for women who do develop breast cancers (drugs like tamoxifen and chemotherapy) and more self-awareness. Today, perhaps compared to 25 years ago, women have a heightened awareness of breast health and would be much quicker to see their doctor if they notice something unusual. I’d add a third reason: women are now not taking estrogen for menopause as they did for decades believing it prevents heart attacks or cancers. The single biggest cause of the reduction in breast cancer deaths in the last decade is the fact women have largely stopped taking a drug that was causing breast cancer!

Yet the popularity of mammography persists, kept aloft by almost a half-century of promotion, hype and overpromises. The advocates, those women who say they owe their lives to screening, as well as health professionals – mainly radiologists and others who have benefited from this aspect of the ‘war on cancer’ for the last few decades – can be particularly nasty in their criticism of people like Peter Gotzsche, Anthony Miller or Cornelia Baines.

The recent BMJ publication drew out all kinds of invective and poison directed at Cornelia Baines and her colleagues. Even the BMJ, one of the world’s most respected medical journals, was accused of being a “leading mouthpiece of anti-mammography articles” and Peter Gotzsche was labelled “the most vocal and prolific anti-mammography voice out there.” One writer said he is already responsible for the deaths of thousands of Danish women due to his views and that “Thousands more women will die worldwide if they and their providers believe the lies that you are spreading.”

Researchers like Cornelia Baines, who has been accused of carrying out a “personal vendetta against mammography” has faced harassment and distortion of her data for over two decades. One particularly poisonous email sent to her and colleague Anthony Miller from two prominent radiologists said, “May the faces of the thousands of women who have died, and will continue to die, prematurely because of you, continue to haunt you in your dreams, and in your nightmares.”

It has taken a long time, but the world is finally starting to vindicate what these researchers have been saying.

In fact, as I sat down to write this (mid-April, 2014), an article was published in the New England Journal of Medicine this week that seemed to answer the question Peter Gotzsche asked nearly three years ago about which country was going to be the first to stop mammography screening.

It could be the Swiss might be the first to dismantle systematic breast cancer screening. In a report prepared by the Swiss Medical Board (a group that assesses medical technology), the authors wrote that mammography screening may prevent one death out of every 1,000 screened women, but there was no proof that screening programs affect overall deaths. In other words, echoing the work of Baines, Miller and Gotzsche, the mantra that “Mammography saves lives” is simply not true.

The authors of that article concluded by saying, ”It is easy to promote mammography screening if the majority of women believe that it prevents or reduces the risk of getting breast cancer and saves many lives through early detection of aggressive tumours. We would be in favour of mammography screening if these beliefs were valid. Unfortunately, they are not and we believe that women need to be told so.”

I was essentially saying the same thing when I published Seeking Sickness two years ago. You can try to push an agenda and a belief system, but, at the end of the day, clear, unbiased information which promotes the right care for the right patient and avoids overdiagnosis and overtreatment is the best path of all.

Alan Cassels is a pharmaceutical policy researcher and the author of Seeking Sickness: Medical Screening and the Misguided Hunt for Disease, which has an entire chapter devoted to the breast cancer screening debate.

3 thoughts on “Mammography’s days numbered”

  1. Mr. Alan Cassels has a bias against early detection to promote his anti-screening book; he also admires Dr. Gøtzsche from Denmark who has a published bias against “all forms of screening” (Lancet 1997). Dr. Gøtzsche has never had access to individual patient data, he does not know which woman was or was not screened, or, even if a breast cancer was diagnosed in a woman who did or did not get a mammogram. How can one assess the impact of screening then? He and Dr. Welch from the USA offer women statistical manipulation weakened by missing facts. Why do these people want to throw women back to the Middle Ages when all breast cancers were huge, often ulcerated and most of them died from the disease. These gentlemen and Dr. Tony Miller, the leader of the flawed “Canadian trials” (trials considered by Prof Paula Gordon from Vancouver a “national embarrassment”) never mention the eight properly carried out randomized controlled trials that unequivocally proved that early detection decreases breast cancer death significantly. I wonder why the anti-screening campaign comes from a country with a shameful “study” and from Denmark where breast cancer death is the third highest in Europe. Something must be wrong with these people; we expect women stand up for their cause. We recommend that Mr. Cassels, a pharmaceutical policy researcher restricts his activities to his area of expertise.

    Professor emeritus Laszlo Tabar, MD, FACR(Hon)

  2. Mr. Cassels, a pharmaceutical policy researcher, has weighed in on screening mammography. He does women a disservice. He quotes only the 25-year update of the Canadian National Breast Screening trial, and does not include the fact that this was the ONLY trial of mammography screening that didn’t show decreased mortality. It is an outlier, and in 2002, the World Health Organization determined that it should be disregarded in in future considerations of the benefit of mammography. The flaws in the Canadian trial have been documented ad nauseum. But every 5 years they publish an update and cause a media frenzy and confusion for women.

    When the results of better trials are averaged, women invited to have mammography showed reduced death from breast cancer of 25-30%. More importantly, in women who actually have mammograms (many women invited in trials do not, but are still counted in the mammogram group when deaths are counted!) the mortality reduction is in the 40-50% range.

    But Mr. Cassels, whose declared conflict of interest is in selling his anti-screening book, says that promoting mammography is possibly dangerous. He quotes the harms of overdiagnosis and overtreatment, and cites Dr. Peter Gotschze and the Cochrane review, which have been roundly criticized by authorities in public health, epidemiology and statistics from all over the world because of their manipulation of data. Gotschze cherry-picked studies that supported his hypothesis, and disregarded favourable studies, based on his misunderstanding of the methodology of cluster randomization in screening trials.

    Mammography is not perfect. It doesn’t find all cancers, and when women are recalled when we find something on a mammogram that needs more tests, there is unavoidable transient anxiety and even sometimes a needle biopsy done with freezing to rule out cancer. But women know that this is reasonable, and would choose to have the test rather than let a patronizing administration decide that they should be spared the anxiety, and lose the opportunity to find a small cancer.

    Canadians deserve to hear the truth, not Mr. Cassels slagging the Canadian Breast Cancer Foundation. They appear to have a better understanding of the science than he does. He should stick to his area of expertise.

    Paula Gordon, OBC, MD, FRCPC, FSBI
    Clinical Professor, University of British Columbia

  3. It’s time to end the debate about mammography because there is nothing to debate. There is a 25% reduction in breast cancer mortality amongst women who screen regularly. Mammograms save lives.


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