Mammograms need more scepticism
Last week, a Danish study published in the Annals of Internal Medicine attracted a lot of attention for claiming that one in three tumours detected during mammograms are harmless, meaning that women are often pressed to needlessly undergo potentially harmful cancer treatments. The study reinforces several other papers supporting the possibility that cancer overdiagnosis is widespread.
Radiologists and cancer research groups were quick to push back, arguing the Danish study greatly overestimated false diagnoses and noting that mammograms can catch cancer at its early stages and save lives.
Welcome to one of the most frustrating aspects of health care. There’s so much at stake, and yet so much emotional disagreement. Still, it’s important to note that there’s one thing that just about everyone agrees on: mammograms are far from perfect, and overdiagnosis is a legitimate problem in cancer treatment.
If you care at all about health research, this debate is nothing new. Health experts have long thrown doubt on the efficacy of mammograms, pointing to a pile of studies that suggest they aren’t nearly as effective as we’d hope. One massive 2014 study – reviewing almost 90,000 women aged 40 to 59 in Britain – found no significant difference in cancer deaths between those who received mammograms and those who didn’t. Also, consider that while the United States recommends women receive mammograms way more frequently and at younger ages than women in Europe, the US runs in the middle of the pack among developed countries when it comes to mortality rates.
Part of the problem is that there’s still so much we don’t know about breast cancer. Take, for instance, ductal carcinoma in situ – the most common type of noninvasive breast cancer. Researchers have been studying DCIS for a long time, but simply can’t agree on what it is – and the debate can get pretty bitter.
Some scientists want to consider it a ‘‘pre-cancer’’ or a ‘‘risk of a cancer’’. Others insist that it’s better to be safe than sorry and recommend treating it through surgery and radiation. For patients, the mixed messaging is confusing and frustrating.
So what should a 40-year-old woman do if she has a mammogram and learns that she has DCIS? There isn’t an easy answer. It’s tempting to get wrapped up in the feel-good, Angelina Jolie narratives, but anecdotes are not good science, and no-one should disregard the costs and pains of treatment for an overdiagnosis.
For Aaron Carroll, director of the Center for Health Policy and Professionalism Research at Indiana University School of Medicine, the solution is to recommend that younger women with low risk factors not have
No-one should disregard the costs and pains of treatment for an overdiagnosis.
mammograms done.
The more optimistic take – as outlined by Otis Brawley of the American Cancer Society in an editorial responding to the Danish study – is to believe that cancer research will let us identify which breast cancers are dangerous and which are not, possibly at the genetic level.
Hopefully, that’s the solution. In the meantime, the message to women should be to temper their expectations of mammograms. Studies show that patients grossly overestimate the power of mammograms to detect and prevent cancers, but this needs to be corrected. We really shouldn’t be overselling how well we understand this disease. — Washington Post