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What should women who are low-risk know about the updated guidelines for breast cancer screening?

February 4, 2019

By Dr. Melinda Wu and Jennifer Lee

The Canadian Task Force on Preventive Health Care released updated guidelines for breast cancer screening in low-risk women aged 40-74 years in December 2018, emphasizing the need for shared decision making between women and their doctors. Dr. Melinda Wu, a family physician, general practitioner in oncology and clinical education lead at the Peter Gilgan Centre for Women’s Cancers breaks down how this applies to women in this group. 

1) When is a woman considered to be not at a higher risk of developing breast cancer?

First, it’s important to look at the factors that do place women at a higher “lifetime risk” of developing breast cancer, which equates to a 20-25 per cent greater risk than the average woman. These can include things like having:

  • a personal history or a first degree family member with genetic mutations such as the BRCA1 and BRCA2 mutation, among others
  • a strong family history of breast cancer that has affected two or more first-degree relatives or three or more relatives from anywhere in your family tree – particularly those that are under 50 years of age or who are premenopausal
  • a personal history of “atypia” or atypical cells found in a breast biopsy
  • a personal history of chest radiation prior to age 30

Outside of this, there are other factors that mildly or moderately increase risk, but taken on their own they are not enough to place someone in the “high risk” category. This can include things like a later onset of your first period (after age 12), having your first child after age 30, the late onset of menopause (after 55 years of age). It can also include lifestyle factors like consuming more than two drinks per day, not exercising or being overweight.

But it’s important to remember that there are many risk factors that are taken into consideration and they may not be “cumulative risks” in the sense that you likely can’t just add up the ones that pertain to you and create a sum of your overall risk. This is why it’s important to sit down with your doctor to talk about your personal health history, as it will help you both make a decision as to whether or not mammogram screening is recommended.

2) The updated guidelines speak about the harms vs. the benefits of breast cancer screening in women who are not at high risk. Can you explain what these are? 

First off, the benefit of screening is the opportunity to diagnose breast cancer early and reduce the need (and consequences of) treatments required for more advanced stages of the disease. It’s also ultimately intended to help reduce the number of women who die from breast cancer.

The harms of breast cancer screening include things like exposure to radiation through mammographic testing, potential discomfort from mammography itself, stress and anxiety related to the process of attending the test and waiting for the result and the potential for false positive or false negative results.

3) Why are women aged 50 and under at greater risk for harms from breast cancer screening than those over age 50?

Breast cancer is less common in premenopausal women, though it definitely does occur. However, women who are under 50 are at increased risk of false positive tests. This is in part due to the fact that before menopause, women tend to have denser breasts. The issue here is that false positive test results can lead to further investigation, like the need for additional imaging or even a biopsy, when these changes wouldn’t have ended up being linked with breast cancer, causing undue stress and anxiety for patients. Additionally, embarking on breast screening earlier than age 50 exposes patients to radiation from mammography, although this is a minimal amount.     

4) What about breast self-exams, why do these guidelines recommend against them?

When done on a routine basis, breast self-exams are thought to lead to an increased number of unnecessary investigations that yield in false positive results. We no longer educate patients in breast self-examination, instead we encourage self-awareness. I often tell patients to get to know their own body as every woman will have a different landscape underlying their breast tissue. For example, the tissue may feel lumpy but should be fairly consistent over time. If you stay familiar with your breasts and how they feel, it’s easier to tell if something new has developed and even if you are uncertain about it, speaking with your doctors to get an assessment is important to decide on next steps.

5) If women are interested in breast cancer screening, what kinds of questions should they come prepared to speak with their doctor about?

Women are encouraged to approach their doctor to discuss what we call their “personal risk factors.” These include having a family history of breast or ovarian cancer, knowing if there is a family history of genetic mutation, a personal history of breast biopsy (and what the results were) or a history of exposure to radiation. As well, it is helpful to know whether you have any Ashkenazi Jewish heritage in your family.

Examples of helpful questions to ask your doctor include things like whether your known risk factors put you at high risk for developing breast cancer, what the benefit or harms of breast cancer screening are, how often should you be getting screening, and what can you do to reduce your risk?

The important change in these new guidelines is that the choice to participate in screening should result from a collaborative discussion between a patient and their doctor. It is important to consider a patient’s perspective and values when it comes to screening and this may ultimately drive whether or not they embark on screening at age 40 to 49, or at any stage.  Family doctors should also be well equipped to handle these discussions, and fortunately we also have GPOs (General Practitioners in Oncology) here at Women’s College Hospital in the Henrietta Banting Breast Centre, who can see patients to have this discussion if they need more support.

The Peter Gilgan Centre for Women’s Cancers at Women College Hospital, in collaboration with the Canadian Cancer Society, draws together excellence in research, clinical care, innovation and education for women’s cancers.



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