Breast cancer screening – when ‘talking to your doctor’ may mislead rather than inform

15 October 2018

Oh boy, October really is the month for ‘health awareness’! Aside from Sleep Awareness Week and World Mental Health Day, October – the entire month – also plays host to Breast Cancer Awareness Month.

Thankfully, Cancer Australia no longer advocates non-evidence based practices such as breast self-examination and clinical breast examination (examination of the breasts by a doctor or a nurse), instead advising women to “get to know the normal look and feel of your breasts as part of your daily routine” so that they notice any changes that may indicate breast cancer.

And the enthusiasm for screening mammography in official messaging about breast cancer has been toned down in recent years, thanks largely to the dogged commitment to evidence-based practice demonstrated by Dr Peter Gøtzsche, founder of the Nordic Cochrane Centre – and recently ejected from Cochrane because of his co-authorship of an article criticising Cochrane’s own review of the human papilloma virus [HPV] vaccine, which, Gøtzsche and his co-authors argued, omitted nearly half of the trials it should have analysed, and was influenced by reporting bias and biased trial designs (not the least of which was the absence of a true control group).

Gøtzsche led the team which published a 2013 Cochrane review which concluded that

“screening [that is, giving women who do not have any signs or symptoms of breast cancer a mammogram to try to detect breast cancer at an earlier stage] did not reduce breast cancer mortality”

… or in plain language, getting regular mammograms does not reduce a woman’s risk of dying from breast cancer.

It gets worse. The Cochrane review continues,

“screening will result in some women getting a cancer diagnosis even though their cancer would not have led to death or sickness [overdiagnosis]. Currently, it is not possible to tell which women these are, and they are therefore likely to have breasts or lumps removed and to receive radiotherapy unnecessarily [overtreatment]. If we assume that screening reduces breast cancer mortality by 15% after 13 years of follow-up and that overdiagnosis and overtreatment is at 30%, it means 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. Furthermore, more than 200 women will experience important psychological distress including anxiety and uncertainty for years because of false positive findings… Recent observational studies show more overdiagnosis than in the trials and very little or no reduction in the incidence of advanced cancers with screening.”

Cochrane’s plain-language brochure for patients spells it out clearly: 2000 women need have to have regular mammograms for 10 years to prevent just one of them from dying of breast cancer, but in that time, 10 of those 2000 women will have been diagnosed and treated unnecessarily for a ‘cancer’ that would never have become apparent in their lifetime, and would not have killed them.

Official advice on screening mammography has now backed away from the false reassurance that getting a mammogram will ‘save your life’ (it won’t; even the US Preventive Services Task Force, which recommends that women aged 50-74 have mammograms every 2 years found that “none of the trials nor the combined meta-analysis demonstrated a difference in all-cause mortality with screening mammography” – that is, the tiny number of women who didn’t die of breast cancer because they had a screening mammogram don’t actually live any longer despite being successfully treated for breast cancer).

Women aged 50-74 are now directed to “talk to your doctor about what mammography screening involves and the possible outcomes”, while women aged 40-49 are warned that mammograms are not as effective in their age group as for 50-74 year olds.

The constant refrain in all of the advice given is that women should “talk to their doctor” to help them make the decision about whether to undergo screening mammography. The assumption underlying this recommendation is that doctors can and will give objective advice to their patients, based solely on consideration of their medical and family history, and personal risk factors.

However, research published in JAMA Internal Medicine indicates that doctors are just as likely as patients to rely in their decision making on “anecdotal information about breast cancer screening fundamentally different from—and potentially at odds with—scientific evidence that relies on estimates of mortality reduction”.

The researchers surveyed US general practitioners and gynaecologists about their breast cancer screening practices. The doctors were also asked about female members of their social network (patient and friends or family members) who had been diagnosed with breast cancer, and whose diagnoses had had the biggest impact on them. They were also asked whether the cancers had been detected by screening mammography, and whether the affected women had a good or poor prognosis.

Whereas only 6% of US women with breast cancer are diagnosed with advanced disease, doctors were more likely to recall such cases than those of women with good prognoses. As the researchers commented, “disproportionate recall of these bad experiences is in line with the abundant behavioral literature that highlights how dreaded outcomes are more easily remembered, which can increase perceived risk.”

Furthermore, doctors who recounted knowing a woman whose breast cancer was not diagnosed by screening mammogram and who had a poor prognosis had an increased likelihood of recommending routine screening to patients in age groups for which evidence-based guidelines no longer support this practice.

The tendency of doctors to ignore evidence when their emotions are activated is not exclusive to decisions around mammography screening. Dr John Mandrola’s account of his debate with a fellow cardiologist on the value of percutaneous coronary intervention (PCI – angioplasty with or without stenting) in patients with stable coronary artery disease, is a sobering read.

In front of an audience that included experienced doctors from all specialties of medicine and surgery, Mandrola presented the findings of over 60 studies, dating from the 1990s onward, that PCI does not save lives in any group of patients, outside of an acute situation (i.e. when a person is having a heart attack), and, shockingly, does not even reduce angina – the chest pain associated with coronary artery disease.

His opponent presented no evidence whatsoever. Instead, he showed the audience angiograms of “scary looking blockages”, and recounted anecdotes of patients with 90% blocked arteries who presented a surgery risk when they presented to the hospital for some other reason, such as gallstones.

Shockingly, when the audience of medical professionals was asked whether they would want medical therapy alone or a stent if they were affected by stable coronary artery disease, nearly the entire audience indicated that they would opt for the stent – despite a total lack of evidence for its effectiveness.

Mandrola pondered to himself,

“Why don’t my colleagues realize that anecdotes even out in trials of thousands of patients? The whole reason for doing randomized controlled trials is so we are not fooled by our own biases.”

He went on to reflect,

“I thought that since doctors were trained in science and reason they could be persuaded by evidence. Maybe the German physicist Max Planck was correct when he implied science only advances one funeral at a time.”

Unfortunately, in many cases, medical intervention may hasten the patient’s funeral. Before “talking to your doctor” about undergoing any kind of diagnostic procedure or treatment intervention, it’s wise to do your own research using reputable sources of medical information such as Cochrane reviews (at least, those conducted prior to the last couple of years, when Cochrane began accepting funding from sources that have compromised its independence and integrity) and The NNT.

While PubMed is a great starting point for researching any medical or health topic (and Sci-Hub gives you free access to the vast majority of studies published in peer reviewed medical journals), be aware that single studies don’t prove the case for or against any diagnostic or treatment procedure, and the weight of evidence needs to be taken into account.

It goes without saying that unreferenced blogs and books that simply report individuals’ anecdotal experience do not count as scientific evidence, as Dr Mandrola pointed out.

In my EmpowerEd health education program, I train members to understand and assess scientific studies so that they can have intelligent, informed discussions on diagnostic and treatment options with their medical providers. My detailed, fully referenced webinar ‘Cancer Screening’ is available to watch as soon as you activate your 1 month free trial of EmpowerEd membership.