The Controversy of Breast Cancer Screening — what you didn’t know.

Confused about whether to have a mammogram for breast cancer screening? Already had a mammogram, but you’re not sure when to have your next? Head spinning about when to start, how often, and even when to stop? Well, you are not alone. With major medical organizations promulgating guidelines sometimes at odds with each other, this subject is confusing, and may I add, even to health care professionals. Individual physicians are known to offer differing screening schedules depending on his or her specialty. For example, did your Ob-Gyn recommend one thing only to have your Family Physician or Internist recommend another?

What is breast cancer screening anyway?

Screening is an exam or test that is performed to determine if a condition is present in a person who has no related symptoms. In the case of breast cancer screening, that screening test is a mammogram also referred to as mammography. If you have a lump or another problem in your breast, testing is no longer considered screening. Although the test may still be the same, it is referred to as “diagnostic” rather than “screening,” and this discussion does not apply to you. If you have breast symptoms (such as a lump) let your doctor know immediately regardless of your age or risks. In addition, this discussion is only for “Average Risk Women.” Consequently, this discussion does not apply if you are in a higher risk category for developing breast cancer. These risk factors include the conditions listed below, so regardless of your age, be sure to talk with your doctor, if you have any of the following health history:

• Personal or family history of breast or ovarian cancer in first degree relative or multiple family members
• Personal History of Cancer or Precancerous Conditions of the Breast
• Genetic mutations such as BrCa
• History of Radiation to the Chest
• Postmenopausal Hormone Therapy
• Being an African American woman

For those who have not experienced a mammogram yet, it’s a good idea to understand what the process entails. A mammogram is essentially a low-dose X-ray picture of the breast, using a special machine that compresses the breasts to spread out the breast. The flattening will cause some discomfort such as pinching and squeezing, but don’t be alarmed — it only lasts a few seconds! The Office on Women’s Health of the US Department of Health and Human Services (HHS) describes the process nicely in their fact sheet.

What is the evidence behind breast cancer screening?

Before reviewing screening guidelines, it’s worth understanding the research behind the recommendations, their variance and why there is controversy. The US landmark study demonstrating that breast cancer screening with mammography saved lives was published in 1997 in the Journal of the National Cancer Institute and showed a 25% reduction in breast cancer mortality. In this study, the Health Insurance Plan of Greater New York (HIP) between 1963 and 1967 enrolled close to 60,000 women 40–64 years of age and followed them for up to 18 years. The authors found a clear benefit in all age groups. However, most of the women who entered the study in their 40s, and were ultimately diagnosed with breast cancer, were actually diagnosed in their 50s. Thus, the study supported the value of screening women in their 50s and 60s while questioning the utility of screening women in their 40s. The results of this study have served as the foundation for breast cancer screening in this country for more than 2 decades. Under ordinary circumstances, widespread management guidelines are not adopted based on a single study. However, based on the enormity of the study and significant mortality benefit established, a repeat study using a control arm in which women do not undergo a mammogram was considered unethical, and has never been performed. Controlled studies have been performed in other countries though, as you will later read.

Other data that are used to support population-based breast cancer screening come from the National Institutes of Health (NIH) referred to as the Surveillance, Epidemiology and End Results Program (SEER). These reveal a reduction in breast cancer mortality over the past several decades. While proponents of mammography like to believe that the decrease in death rate is due at least partially to screening, other experts debate whether screening has made any contribution. Some point to new and effective treatments as the cause of the observed reduction in breast cancer mortality, while others more conservatively attribute the decrease to the combination of early diagnosis and improved therapies.

If the HIP study demonstrated that screening achieved a statistically significant 25% reduction in breast cancer mortality, and the NIH shows death from breast cancer deaths have gone down over roughly the same time period, why is there controversy?

Although no further controlled studies have been performed in the US, other industrialized countries have undertaken their own. For example, the Canadian Breast Cancer Screening study published in the Annals of Internal Medicine in 2002 failed to demonstrate a reduction in death rate among women ages 40–49 who were followed for up to 16 years. Similarly, no benefit was found in women ages 50–59 at the 13 year follow-up published in 2000 in the Journal of the National Cancer Institute.

At the 25 year follow-up of the 2 Canadian studies, published in 2014 in the British Medical Journal, the authors reported “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”. However, strong proponents of screening rejected these results and in their vitriolic responses accused the authors of “shoddy research,” flawed methodology and “going back to the dark ages.”

Findings were also mixed outside of North America. Following implementation of widespread screening programs in Norway, a statistically non-significant difference in mortality of 11% was demonstrated and published in 2012. While the Swedish Population Study 2011 reported a statistically significant benefit from screening of 27% reduction in breast cancer mortality over a period of 3 decades, in a separate analysis of the Swedish data, the authors concluded that “County-specific mortality statistics in Sweden are consistent with studies that have reported limited or no impact of screening on mortality from breast cancer”.

And in the Netherlands, a non-randomized population screening study showed a gradual decrease in breast cancer mortality since 1997 prior to which mortality had been stable. However they were cautious in their conclusions and reluctant to attribute benefit solely to screening, understanding that during that period, breast cancer awareness had increased and treatments had dramatically improved.

In the UK a cohort study conducted between 1991 and 2005 found that an invitation to screening (compared to not being invited) was associated with a statistically significant reduction in breast cancer mortality in of 21%.

Finally, an Australian screening study published in 2008 found that participation in screening was associated with a breast-cancer mortality reduction of between 30 and 41%. However, concern regarding an evolving concept referred to as “overdiagnosis” of breast cancer led the Australian government to publish a position paper updated in 2014 on their guidelines for screening. Their position paper highlights this concept of overdiagnosis which has not been as universally considered in the US. More on this later.

A 2012 paper entitled Effect of Three Decades of Screening Mammography on Breast Cancer Incidence published in the New England Journal of Medicine concluded that “Despite substantial increases in the number of cases of early-stage breast cancer detected, screening mammography has only marginally reduced the rate at which women present with advanced cancer. Although it is not certain which women have been affected, the imbalance suggests that there is substantial overdiagnosis, accounting for nearly a third of all newly diagnosed breast cancers, and that screening is having, at best, only a small effect on the rate of death from breast cancer.”

Then in their 2014 82-page position paper, the World Health Organization (WHO) went on to recommend women age 50–69 be screened every 2 years, “if shared decision-making strategies are implemented so that women’s decisions are consistent with their values and preferences”. They recommended the same for the younger and older groups (40–49 and 70+), but admitted that there was less benefit in these groups. The WHO reports that overdiagnosis ranged from from 0% to 54% in studies they reviewed.

In 2015, the International Agency for Research on Cancer (IARC), the cancer research arm of the WHO published their viewpoint in the New England Journal of Medicine. They concluded that screening women ages 50–69 provided “net benefit” of reduced mortality in women ages 50–74, but that the strength of the evidence for women in their 40s was “limited.” They commented that adding mammography to routinely and competently performed self-breast exam had not been shown to improve outcomes. They once again raised the concern of significant overdiagnosis.

The Cochrane Database Systematic Review published a meta-analysis in 2013 in which the authors performed a review of 8 trials. The combined relative risk reduction was 19% with the caveat that they did not find an effect of screening on total cancer mortality or “all-cause” mortality.

As a result of their findings, the authors published to the lay public their recommendations regarding the benefits and harms of screening in a leaflet. This leaflet has been translated into more than 16 languages and distributed globally. They report on the significant harms of mammographic screening, most notably that of overdiagnosis resulting in unnecessary treatment, and that these harms are underestimated in most guidelines.

And just last month a study from Denmark was published as the lead article in the Annals of Internal Medicine in which the authors concurred that screening did not reduce the incidence of advanced cancers; i.e. despite screening, women were still being diagnosed with advanced cancer. Furthermore, the study concluded that 1 in every 3 invasive and non-invasive tumors likely represented overdiagnosis.

The NIH’s National Cancer Institute (NCI) discuss harms of screening listing overdiagnosis as their top concern. They explain there are some breast cancers being diagnosed with mammography that are “insignificant” and would never have caused any problem had they not been diagnosed via screening. It’s hard to imagine, but it turns out that some cancers never grow, metastasize or cause harm. On occasion small cancers even regress. Currently, we have no way of testing and therefore no way of knowing, and no scientific crystal ball to tell us if a cancer will grow or eventually metastasize. The NCI suggests that the diagnosis and treatment of cancers that would never have caused harm is harmful (it is), but current methods do not allow us to determine which will and which will not progress.

So, what are the recommendations?

Up-to-Date, a leading clinical resource for physicians and academic medical centers worldwide synthesizes the recommendations into a simple-to-read table. The CDC publishes a similar reference of guidelines and recommendations from 10 respected medical organizations in the world, including 5 American medical specialty societies, the USPSTF, the NCCN, and the Canadian, British and Australian national health services.

Despite the controversy over harms and benefits, all groups continue to endorse screening mammography because so much of the data support the benefit and that early diagnosis, leading to improved survival, while not convincingly proven to all, seems so logical and intuitive. All groups are in agreement that women aged 50–74 will likely benefit from screening. Their recommended screening intervals range from every one to two years. All groups agree that no screening be done in average risk women younger than 40, as there is no evidence of benefit in that group. Controversy persists in regard to the benefit for women in their 40s and women older than 74, resulting in the shared decision-making recommendation for these groups.

And, what do I recommend?

There is no doubt that my recommendations and those of the other providers at Carbon Health are based on our beliefs that despite some evidence to the contrary, the benefits of screening outweigh the risks and potential harms as we now know them. As the second leading cause of cancer death in women after lung cancer, it’s worth using current modalities to reduce mortality until we discover a better means. The modality that is available to us now is the mammogram. My personal preference for screening is aligned with the USPSTF recommendation, which I believe takes a more circumspect approach balancing the pros and cons. I highly recommend reading the thoughtful and easy to follow pamphlet published by the Australian government that visually explains the benefits and harms of screening. Ultimately, you should decide what guidelines apply to you — with the help of a healthcare provider you trust.

With this detailed overview of the evidence regarding breast cancer screening, you too can join in the debate on the benefits and harms of screening. If you are a mammogram-eligible woman, hopefully you now feel equipped to make a more informed decision in consultation with your physician about what is appropriate for your individual situation. Mammography screening has been deeply rooted for decades into our country’s psyche and healthcare system, and the varying guidelines around screening are not likely to change anytime soon regardless of the downside. While overdiagnosis due to screening may not disappear tomorrow, with a greater understanding of genetics, immunology and cancer cell biology, I envision a day when treatment will be directed only at high risk disease, thus avoiding overtreatment.

We at Carbon Health believe the best approach is evidence-based and individualized based on your risks, level of concerns and comfort with undergoing mammograms. We practice the shared decision-making model where your preferences and values will guide the outcome. If you would like to discuss what is best for you in breast cancer screening, feel free to reach out today via video chat, text or at our clinic.

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