On the futility of breast cancer screening

Breast cancer screening doesn't save lives, doesn't 'catch cancer early', and doesn't protect women from aggressive treatment. So why are we still spending great gobs of money on it?

One of the principal load-bearing myths on which the sociopolitical power of the medical-industrial complex rests, is that cancer screening programs save lives. It seems intuitively obvious that if cancer is detected at an early stage when it is smaller, less aggressive, and hasn't metastasised, it will be easier to treat, and hence patients will be subjected to less aggressive treatment protocols and will be more likely to survive their brush with 'The Big C' than if their cancer was only diagnosed when it had reached a more advanced stage.

The axiom that catching cancer early leads to better treatment outcomes, including lower mortality, undergirds the heavy marketing of cancer screening programs - such as PSA testing, skin cancer checks, screening mammography and screening colonoscopy - to the public. It's also the premise behind the promotion of liquid biopsy or circulating tumour cell tests for cancer screening of the 'worried well'.

The fly in the ointment is, as I wrote in Major study finds that cancer screening programs don’t extend life, that there's just no convincing evidence that any cancer screening program saves lives. Screening mammography does not reduce either breast cancer-specific or overall mortality. PSA screening does not reduce either prostate cancer-specific or overall mortality. Screening colonoscopy does not reduce either colorectal cancer-specific or overall mortality. Visual skin examinations by clinicians do not reduce skin cancer-specific or overall mortality. Cervical cancer screening does appear to reduce the risk of dying from cervical cancer, but its effects on overall mortality are uncertain.

And yet, no matter how many papers on the demonstrable failure of cancer screening programs to 'save lives' get published in high-impact peer-reviewed medical journals, doctors, public health agencies and cancer charities continue to promote screening programs, and patients continue to participate in them. What will it take to bust this load-bearing myth, once and for all? I wish I knew. There's bugger-all evidence that vaccines reduce mortality from infectious disease and some concerning indications that the more doses of vaccine given, the higher the rate of early childhood mortality, yet the myth that vaccination has saved countless millions of lives still persists, like an undead zombie that just can't be killed.

But for what it's worth, yet another study has been published which attacks the foundational premise of breast cancer screening: the notion that by detecting tumours at an early stage, screening mammography reduces the risk of invasive breast cancer which requires more aggressive treatment and is more deadly. The background to the study is that in 2009, the US Preventive Services Task Force (USPSTF) updated its breast screening guidelines. Prior to this update, all US women aged over 40 had been advised to undergo screening mammography every one to two years. The revised guidelines recommended individualised decision-making for women aged 40-49, biennial (once every two years) screening for women aged 50-74, and no screening for women aged 75 and over. And it appears that the guidelines made an impact; there was "an immediate and significant decrease in screening mammography rates" after 2009.

Predictably, advocates of screening mammography had conniptions. Reduced frequency of screening, they insisted, would result in more women being diagnosed with larger and later-stage tumours, necessitating more invasive surgery and more aggressive treatment. Again, this seems intuitively obvious... but were their fears justified?

To find out, researchers from the University of Vermont in Burlington analysed breast cancer incidence data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program (SEER). Specifically, they compared both the breast cancer stage at the time of diagnosis, and the type of surgical treatment given, in women aged 40 years and over who were diagnosed with primary breast cancer in the five years prior to the USPSTF guideline update, vs those diagnosed in the ten years following it.

The stages of breast cancer diagnosis that they used, in ascending order of clinical severity, were:

• In situ (noninvasive, ductal, or lobular);

• Localised (confined to breast tissue);

• Regional (lymph node involvement or direct extension to pectoral muscle, chest wall, or skin); and

• Distant (metastatic).

The surgical interventions considered were partial mastectomy (also known as lumpectomy), total mastectomy, and total mastectomy with reconstruction.

In all, data from over two million women with a breast cancer diagnosis were eligible for analysis. The major findings were as follows:

1. Rates of diagnosis of in situ breast cancer increased before 2009 in all age groups, and then decreased after the USPSTF guideline change.

This is a completely predictable finding. As I explained in Major trial finds screening colonoscopy fails to ‘save lives’,

"H. Gilbert Welch uses the ‘barnyard pen of cancers’ analogy to characterise the highly heterogeneous grab-bag of diagnoses collectively labelled ‘cancer’, into three types of animal, with the fence representing screening:

• ‘Birds’ represent the most lethal type of cancer. No fence can contain them; they simply fly away. By the time ‘bird’ cancers are detected, they’ve already spread around the body, invading vital organs. Conventional cancer treatments hold no hope of cure; at best, life may be prolonged by surgery, chemotherapy, radiation or immunotherapy, but at the cost of side-effects that dramatically reduce quality of life.

• ‘Rabbits’ could be contained if you build enough fences. Catching ‘rabbits’ is the mainstay of cancer screening. This would be worthwhile if ‘rabbit’ cancers would have gone on to cause life-threatening illness if they had not been detected, but research indicates that this is rarely the case. In the small minority of people in whom screening caught a ‘rabbit’ that would have gone on to kill them, detecting it early would only be of benefit if the treatments for that cancer type were effective at curing it, and did not cause harms that outweigh their benefits. By the time we apply all these criteria, we’re in unicorn land.

• ‘Turtles’ can easily be contained by fencing, but since they weren’t going anywhere anyway, there’s no point in putting the effort into building the fence.

It’s the ‘turtles’ and ‘rabbits’ that are most likely to be detected by cancer screening. Hence, cancer screening results in considerable overdiagnosis – that is, many people are told that they ‘have cancer’, and undergo aggressive treatment which may lead to lifespan-shortening health problems (including, ironically enough, cancer), for a tumour which would never have led to serious illness or death if it had remained undetected."

Major trial finds screening colonoscopy fails to ‘save lives’

So, under the pre-2009 guidelines which recommended more frequent screening mammography, more women were diagnosed with and treated for a condition that probably shouldn't be called cancer at all; after that 2009 update, rates of this manifestation of overdiagnosis declined.

2. Rates of diagnosis of localised breast cancer steadily increased from 2004 to 2019 in women aged 40-74, fluctuated in women aged 75 and over, and most importantly, showed no trend in relation to the change in screening guidelines.

3. Rates of diagnosis of regional cancer decreased after 2004 in all age groups, and again, showed no trend in relation to the change in screening guidelines.

4. Rates of diagnosis of distant cancer increased before 2009 in women aged 40-49, before 2012 in women aged 50-74, and over the entire study period (2004-2019) in women aged 75 and over and, once again, showed no trend in relation to the change in screening guidelines.

Figure 1. Breast Cancer Incidence by Age at Diagnosis Within the Surveillance, Epidemiology, and End Results 21 Registries, 2004-2019. From Changes to the US Preventive Services Task Force Screening Guidelines and Incidence of Breast Cancer.

5. There were changes in the rates of partial vs total mastectomies that varied somewhat by age group, with a trend toward less invasive surgical procedures after 2012; once again, these changes showed no relationship with the timing of the guideline change.

In other words, reduced frequency of breast screening, and reduced identification and treatment of in situ cancer, did not result in more women being diagnosed at a later stage, necessitating more aggressive surgical treatment. It's worth quoting the authors of the study at length, not least because they were somewhat surprised by what they found:

"In situ breast cancer is predominantly detected on mammography screening.¹³ The decreases we observed in in situ breast cancer incidence are consistent with the decreases in screening use observed after the 2009 USPSTF screening guideline changes.^3-6 With this decrease in in situ breast cancer diagnoses since 2009, we anticipated that a proportion of undetected in situ breast cancer would progress, potentially contributing to an increasing incidence of localized breast cancers starting after 2009. However, we observed no discrete shifts in localized cancer incidence trends after 2009; rather, there was a steady continued increase in localized breast cancer consistent with the pattern observed before 2009. A possible exception was observed in women aged 75 years or older, among whom localized invasive cancer incidence increased beginning in 2017 after a period of decreasing in situ breast cancer incidence and stable localized invasive cancer incidence. However, this would require a long sojourn time (≥9 years) to progression to be attributed to the decrease in in situ breast cancer incidence that began in 2008.

With the substantial decreases in screening in women aged 40 to 49 years,^3-5 we would also anticipate increases in regional and distant cancers in that age group after 2009, which were not seen. There was no evidence for an increase in regional cancers across any age group. Women aged 75 years or older⁶ experienced an increasing incidence of distant stage cancers during the study period, but the trend began in 2004, well before the 2009 guideline changes. Overall, there was no clear evidence that reductions in screening and in situ breast cancer diagnoses translated to an increasing incidence of more advanced-stage disease during the study period.

Regarding surgical treatment, there did not appear to be strong evidence that the 2009 screening guideline changes contributed to more aggressive surgical management for in situ, localized invasive, or regional breast cancer. With less screening, we anticipated larger in situ tumor sizes, leading to more total mastectomies, because larger tumors may render some patients ineligible for breast-conserving therapy. There was a trend toward increased total mastectomy and reconstruction rates in women aged 40 to 74 years, but the temporality does not fit our predictions because this trend began before 2009 and leveled off by 2013. After 2012, rates of total mastectomy mostly decreased, whereas rates of partial mastectomy increased or remained the same across all age groups and stages. This finding suggests that lower rates of screening may not have led to increasing incidence of larger cancers that necessitated total mastectomy."

Changes to the US Preventive Services Task Force Screening Guidelines and Incidence of Breast Cancer

In short, contrary to the dire predictions of breast screening advocates, reduced screening did not endanger women by missing early-stage, easily-treated cancers and hence allowing them to progress to more aggressive, invasive and life-threatening cancers which required more extensive surgical intervention. And this is not a novel finding. As I discussed in New study on screening mammography shows more harms than benefits, an analysis of the impact of the BreastScreen program and other screening mammography services on breast cancer incidence and mortality in the Australian state of Victoria found no decrease in the incidence of advanced breast cancer after screening mammography programs were introduced... and the same conclusion was reached in the US, Netherlands, Norway and New South Wales.

We now have a veritable mountain of evidence that cancer screening has not lived up to its advocates' promises. It doesn't help us 'catch cancer early' when it's more treatable, and it doesn't save lives. But why not, when its premise seems so completely reasonable? Most likely, because the model of cancer that it is based on is completely wrong.

That model is as follows: All cancers begin as in situ lesions - small collections of wayward cells - and then progress in a stepwise fashion to local, then regional and, finally, distant disease. But, as the aforementioned H. Gilbert Welch explained, in an incisive 2018 editorial which dissected the implications of a 2015 study, Breast Cancer Mortality After a Diagnosis of Ductal Carcinoma In Situ, by Narod and Sopik,

"Narod and Sopik suggest a wildly different paradigm. Local growth and distant metastasis are independent phenomena. Local control of cancer (e.g., efforts to minimize local recurrence) has no effect on its tendency to metastasize. If a cancer is destined to spread to distant sites, it will have already done so.

Call it the 'bad cancers are bad' model. Or, alternatively, 'good cancers are good.'...

Narod and Sopik are not suggesting that size, stage, and nodal status are unassociated with the propensity to metastasize, rather that we have gotten the direction of causality wrong. The conventional model has been that large tumors are more likely to metastasize because they have a large pool of cancer cells to disseminate. Narod and Sopik instead suggest that these tumors became large because they are more aggressive cancers and thus are more likely to metastasize. Large, late-stage, node positive lesions are simply valuable markers for 'badness.'

The corollary is that small, early-stage, node negative lesions are valuable markers for 'goodness.' But not always. Which brings us to the conundrum of DCIS [ductal carcinoma in situ].

It would be simplest if all DCIS was pseudodisease—cancer not destined to ever cause problems for our patients. Most DCIS is pseudodisease, but as Narod documented in earlier work [2], about 3% of women with DCIS will die from breast cancer in the next 20 years. Over half of these women did not experience an in-breast invasive recurrence prior to death.

In other words, bad breast cancers are bad—from the get go.

This phenomenon explains the limited ability of mammography to reduce breast cancer mortality. The lack of value in finding microscopic breast cancers (like DCIS) is one of the least well-recognized findings from the ten randomized trials of mammography. Only one trial addressed this important question, the second Canadian trial [3]. The control group received an annual clinical breast exam: a standardized, thorough (5–15 min per patient) physical exam of the breast generally done by specially trained nurses. The intervention group received the same thorough clinical exam each year plus a mammogram. In other words, Canada 2 tested the additional value of detecting abnormalities that cannot be felt. Given the finding of no difference in breast cancer mortality between the two groups, the lesson is clear: there is no obvious value to finding breast cancers that are so small they cannot be felt (such as most DCIS).

Overdiagnosis is made possible by cancers at the other end of the spectrum. Overdiagnosis is the detection of cancers that are very good–so good that patients would be better off not having them detected. Overdiagnosis doesn’t limit the ability of mammography to reduce breast cancer mortality—instead it’s a side-effect of the effort."

The heterogeneity of cancer

If Welch's analysis is correct - and there's plenty of evidence that it is - then breast cancer screening will, by definition, never be able to deliver on its promises, no matter how fancy the diagnostic technology becomes, or how efficiently or equitably the programs are delivered.

In 2010 - the latest year for which I could find aggregate data - the estimated cost of mammography screening in the United States was a staggering US$7.8 billion. BreastScreen Australia offers free biennial screening mammograms to all women aged 50-74; the program cost taxpayers A$73.88 million in 2020.

It's hard to make any rational argument for the value of breast screening when it doesn't reduce the diagnosis rate of advanced cancers, doesn't protect women from aggressive treatment, and doesn't save lives. But any researcher, guidelines committee, politician or health bureaucrat who proposes even a modest reduction in the scope of screening mammography programs is going to have to stare down a host of vested interests who are doing very nicely out of the status quo. From the trade groups representing the manufacturers of diagnostic technology, to the radiologists who get paid to interpret the mammograms, to the pathology labs that process the biopsies that result from the suspicious mammograms, to the surgeons and radiation oncologists and medical oncologists who treat the women who get diagnosed via mammogram... it's a cancerous Court of King Caractacus.

Even worse, women who've been harmed by screening mammography are often its most enthusiastic advocates. Very few women whose pseudocancers or indolent tumours were detected by breast screening, ever come to understand that they were overdiagnosed with breast cancer, and consequently were subjected to treatment that they didn't need, couldn't possibly benefit from, and may well have suffered life-shortening harm from. Instead, like battered wives returning to their abuser, they continue to believe that screening 'saved their life'.

If our health care policy actually made any sense, we'd stop wasting time, money and healthcare resources on the fool's errand of 'early detection' programs, and instead educate women on how to reduce their risk of developing breast cancer in the first place. Yeah, I hear those flying piggies too. But while I can't stop the government from flushing my taxpayer's dollars down the cancer screening toilet, I can take responsibility for my own health, and so can you. Eating a diet of whole natural foods (mostly plants, and including traditional soy foods), staying physically active, maintaining a healthy body weight and composition, avoiding smoking and alcohol, and steering clear of estrogenic drugs and chemicals all help to reduce the risk that you'll ever hear the words that no woman wants to hear: "I'm sorry, but you have breast cancer."

For information on my private practice, please visit Empower Total Health. I am a Certified Lifestyle Medicine Practitioner, with an ND, GDCouns, BHSc(Hons) and Fellowship of the Australasian Society of Lifestyle Medicine.