Screening Methods

Screening for Canadian Women with Dense Breasts

The following screening tests are described below:  Mammography, Ultrasound, 3D Ultrasound (ABUS), MRI, Tomosynthesis and Contrast Enhanced Mammography.  Availability widely depends on location.

Why is additional screening needed?

Mammography reduces mortality from breast cancer, but it is an imperfect screening tool for women with dense breasts because it can miss cancerous tumors in dense breasts.

Mammograms can miss cancer about 40% of the time in the densest breasts. Therefore, women with dense breasts might want to consider additional screening with their mammogram. Ultrasound or MRI, when combined with mammography, significantly improves the rate of cancer detection in women with dense breasts.

In Nova Scotia, additional screening is not easily accessed. You may need to advocate for yourself.

Mammography

What it is: Mammography x-rays the breast from different angles. A mammogram is the only way to find out breast density.  

Positives:  Over the past 30 years, mammography has helped reduce deaths through early detection by more than 35%.  Mammograms can detect cancer 2-3 years before it can be felt.

Limitations: For women with dense breasts, dense tissue and cancer appear white on a mammogram, making it hard for cancer to be seen. Mammography uses low-dose radiation.

Accessibility: Screening mammography for women without symptoms (asymptomatic) is available in Nova Scotia and should be booked without a referral, annually ages 40-49.  Age 50-74 is available without a referral every two years, or more often if there are other factors that might increase risk.  Asymptomatic trans women who have taken gender-affirming hormones for at least five years and trans men who still have breast/chest tissue are eligible for the screening program.  

Ultrasound

What it is: Ultrasound uses high frequency sound waves to image the breast. 

Positives: It detects an additional 2-3 cancers per 1000 women. It can detect cancer in dense breasts at an early stage. It is quick, safe, and non- invasive. No radiation is involved.   

Limitations: Ultrasound is a very sensitive test and is generally used for diagnostic purposes, not screening. It may identify abnormalities that require additional investigation. Ultrasound alone is not recommended as a breast cancer screening tool.   

Accessibility: Screening ultrasound is not allowed in Nova Scotia.  Ultrasound is not usually given unless there has been a suspicious finding on a mammogram, MRI or a clinical breast exam.  

Private Clinics: There are no private clinics in Nova Scotia offering breast ultrasound or MRI. 

Automated Breast Ultrasound (ABUS)-3D Ultrasound 

What it is: This is a 3D ultrasound. Sound waves and software reconstruct breast images in a 3D plane.

Positives: ABUS can find small, invasive, node-negative cancers missed by mammography. It is radiation free.

Limitations: ABUS may identify abnormalities that are not seen on a mammogram. Some of these abnormalities may require additional ultrasound or biopsy. Remember most abnormalities are not cancerous.

Accessibility: It is not available in Nova Scotia.

Private Clinics:  In Ontario, there is one location in Toronto that performs screening ultrasound with ABUS. The clinic performs breast imaging and more and is called Toronto Centre for Medical Imaging. Patients wanting ABUS must pay out of pocket but some private/group insurance plans may cover part of the cost. No requisition is needed, but it is recommended to bring a CD with your latest mammograms (unless you are on Pocket Health and can email it) We are not affiliated with the clinic, so please direct any questions to them.

MRI

What it is: MRI uses magnetic fields, radio frequency pulses, and a computer to produce detailed images of the body. Some areas can be seen well without intravenous (IV), but looking for breast cancer requires IV.

Positives:  MRI can be beneficial for women with dense breasts. It can detect cancers when they’re small, help with breast cancer surgical decisions, and ongoing surveillance after breast cancer.

Early detection of breast cancer:

MRI can detect cancers missed on mammograms due to dense breasts. MRI has been proven in many studies to detect invasive cancers while they are still small and have not spread, reduce interval cancers and late-stage disease. MRI significantly outperforms ultrasound in this regard.

Mammograms typically detect about 5 cancers per thousand women, adding ultrasound finds an additional 2-7 per thousand, while MRI can find an additional 12-16 per thousand. Early detection of breast cancer reduces the need for mastectomy and chemotherapy, sparing women from toxic effects and long-term side effects like neuropathy, heart issues, and brain fog.

Limitations: MRI is extremely sensitive and generates more false alarms requiring needle biopsy. It is not well-tolerated by patients who are claustrophobic. MRI requires intravenous contrast injection called Gadolinium. The FDA has released statements on the use of Gadolinium and it is not clear what the impact of Gadolinium is at this time. 

Accessibility: MRI is only available for screening purposes for women who reach the criteria to be included in the high risk program.  A patient may be considered high risk if they have any of the following criteria:  BRCA gene, declined genetic testing and is a first-degree relative of a known mutation carrier, history of chest radiation before age 30* or have a high life time risk of 25% or greater by a standard risk model, e.g. IBIS, BOADICEA.  Find more details on the Nova Scotia Breast Screening Program website.  *In FAQ, it states 25-29 are eligible as well.  To calculate your risk, the IBIS tool can be found HERE.  

Private Clinic:  The closest private pay MRI clinic that does breast is in Moncton, at "IRM Moncton MRI" for a cost of roughly $1000.  (January 2025)  We are not affiliated with the clinic, so please direct any questions to them.  If you go, we'd love to hear about your experience!

Tomosynthesis

What it is: Also known as 3D mammography, it creates multiple thin slices of images so that overlapping tissue is less likely to hide a cancerous tumour. The patient is positioned exactly the same way as for standard mammography.

Positives: Tomosynthesis increases the detection of invasive tumours over digital mammogram by an additional 1-2 cancers per 1000 women.  When used with mammography, it decreases the false positive rate.

Limitations: Tomosynthesis does not detect as many cancers in dense breasts as ultrasound. The radiation dose may be higher than regular mammography because image acquisition takes longer. When used along with regular mammography, the radiation dose is slightly more than double.

Accessibility: Currently, Tomosynthesis is mostly being used for diagnostic purposes after an abnormality is found. It is only available in certain clinics in Nova Scotia.  Clinical studies are taking place in Canada to evaluate the role of tomosynthesis in screening for breast cancer.

Private Clinic:  No

Contrast Enhanced Mammography 

What it is: A standard iodinated contrast agent is used; the same contrast used for CT scans. Cancer cells take up the contrast agent, which absorbs X-rays, so the cancer appears white on the mammogram. 

Positives: Is lower cost than MRI and can detect cancers that are not visible on a standard mammogram. 

Limitations: Uses slightly more radiation than a standard mammogram. Women with poor kidney function or who have had a previous allergic reaction to contrast agents might be advised to avoid this test. 

Accessibility: It is available in limited locations across Canada, such as Ontario, Quebec and British Columbia.  It is not approved for screening by Health Canada yet and is used for diagnostic purposes.  

Private Clinic:  No