Breast cancer screening in Canada 20xx-20xx

Breast screening for individuals at elevated and high risk

Learn more about:

• plans to implement risk-based breast cancer screening
• definitions of elevated risk for breast cancer
• management of participants at elevated risk by screening programs
• definition and data collection for high breast density by screening programs
• data collection of breast density (map)
• definitions of high risk for breast cancer
• management of participants at high risk by screening programs

Individuals at elevated risk are those who are considered to have a greater than average risk for developing breast cancer, but a risk level less than the highest risk group. This may include people who have a family history of breast cancer, have high breast density, used hormone replacement therapy in the past, or are at high risk for benign breast disease. This differs from individuals at high risk who have a greater lifetime risk of developing breast cancer or developing more aggressive breast cancers at an earlier age due to specific factors (e.g., genetics).

Ten provincial/territorial breast screening programs manage participants at elevated risk of developing breast cancer. Some provincial and territorial screening programs define elevated risk as having first-degree family history of breast cancer, using hormone replacement therapy, having a breast density of equal to or over 75%, having a history of high-risk benign breast disease, and having a recommendation by a radiologist. Other provincial and territorial breast screening programs only have one to four of these characteristics listed to define elevated risk. Other characteristics that are listed as risk factors include: having personal or first-degree family history of ovarian cancer, having a first-degree male relative with breast cancer, three or more second-degree family history of breast or ovarian cancer, and documented pathology of high-risk lesions. QC and NB do not classify participants as elevated risk of developing breast cancer. Individuals who are found to be at elevated risk of developing breast cancer are in most cases screened annually with a mammogram, starting at age 40 or 50.

Plans to implement risk-based breast cancer screening

Definitions of elevated risk for breast cancer

_{*Information for NU in this publication refers to opportunistic breast screening.
^ Applies to women who receive a ‘D’ breast density score (BI-RADs category D- extremely dense >75% glandular)}

Management of participants at elevated risk by screening programs

_{* Information for NU in this publication refers to opportunistic breast screening.
^ The OBSP does not use the term “elevated risk”, however, there are several reasons a woman in the OBSP will be recalled by the program in one year: documented pathology of high risk lesions; a personal history of ovarian cancer; two or more first-degree female relatives with breast cancer at any age; one first-degree female relative with breast cancer under age 50; one first-degree relative with ovarian cancer at any age; one male relative with breast cancer at any age; breast density ≥75 percent at the time of screening; or recommendation by the radiologist at the time of screening or assessment
~ Start/stop age is variable depending on conditions for elevated risk designation (e.g. breast density ≥75% may be a transitory condition, therefore start/stop age would be adjusted)
– No information was provided at the time the data were collected.}

Evidence shows that individuals with dense breasts have an increased risk of developing breast cancer, and that having dense breasts can make it more difficult to detect breast cancer by mammogram alone.8 What is not clear, however, is whether more frequent mammographic screening or ‘supplemental screening’ with ultrasound or MRI improves outcomes for these people.7

In Canada, some jurisdictions classify individuals with high breast density as being at elevated risk and, consequently, these individuals are, in most cases, eligible for more frequent screening. Most of these jurisdictions define high breast density as ≥ 75% glandular tissue.

Ten provincial/territorial breast screening programs collect information on breast density. In ON and SK, individuals who have dense breasts receive a breast density fact sheet with their mammography results. Participants are also notified that their next mammogram will be in a year due to dense breast tissue. MB and NL advise individuals of their breast density in the result letter. BC also notifies participants of their breast density. NS began advising individuals of their breast density in their results letter starting in fall 2019, as well as including a breast density fact sheet alongside all results letters.

Definition and data collection for high breast density by screening programs

_{* Information for NU in this publication refers to opportunistic breast screening.
^ Breast Imaging and Reporting Data System (BI-RADS) categories for breast density: A- almost entirely fatty (<25% glandular); B- scattered fibroglandular densities (25-50% glandular); C- heterogeneously dense (51-75% glandular); D- extremely dense (>75% glandular).
~ BC radiologists categorize breast composition using BI-RADS to assess the volume of breast density. The C and D categories are commonly referred to as “dense”. BC Breast Screening currently provides BI-RADS assessment for women and providers; however, it has no definition for “high breast density”.
**Informed that they have dense breasts, but not informed what their dense percentage is
‡Only participants with normal results who have dense breasts, as defined by the program, are informed
– No information was provided at the time the data were collected.}

Data collection of breast density

Individuals at high risk have a greater lifetime risk of developing breast cancer or developing more aggressive breast cancers at an earlier age. Currently, there are no national guidelines for screening individuals at high risk and screening protocols vary across jurisdictions. The definition of high risk of developing breast cancer also varies across Canada.

Definitions of high risk for breast cancer

_{* Information for NU in this publication refers to opportunistic breast screening.
Abbreviations: Atypical Ductal Hyperplasia (ADH)^, Atypical Lobular Hyperplasia (ALH)^, and Lobular Carcinoma in Situ (LCIS)~
^ https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/hyperplasia-of-the-breast-ductal-or-lobular.html
~ https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/lobular-carcinoma-in-situ.html}

Six provincial/territorial breast screening programs manage participants identified as high risk of developing breast cancer. Their management strategies include recommending mammography, MRI and/or ultrasound screening. Some programs do not manage high-risk participants directly but refer those individuals to a high-risk program or clinic. Depending on the province or territory, guidelines recommend that individuals at high risk start screening at age 30, 40 or 50 and stop at age 69 or 74.

Management of participants at high risk by screening programs