Have you noticed that your mammogram reports now include a breast density score?
There are four BI-RADS (Breast Imaging Reporting and Data System) density categories, which range from A to D. Breasts with BI-RADS A density have the least amount of dense tissue and BI-RADS D breasts have the most amount of dense tissue. Breast density can also change over time therefore a patient with BI-RADS category D density on their current mammogram may have a different breast density on their next exam. People with dense breasts have a higher relative risk of breast cancer. Supplemental screening (such as ultrasound or MRI or breast tomosynthesis) detects more cancers in very dense breasts and can be considered as per this recommendation from the Health Quality Ontario supplemental screening page and Cancer Care Ontario (Ontario Health) provider website in English and French.
BI-RADS Breast Density categories A to D
However supplemental screening for BI-RADS D dense breasts is not yet part of the Ontario Breast Screening Program (OBSP). The current OBSP pathways for the finding of Grade D breast density is a repeat mammogram at 1 year instead of 2. As a result:
a. there are no routine automatic supplemental screenings booked
b. the mammogram report for BI-RADS D will likely not include recommendations for supplemental screening
c. Supplemental screening is not performed at all facilities. At facilities that do have access to supplemental screening modalities, resources are allocated based on prioritization according to clinical urgency
Options for possible supplemental screening for BI-RADS D dense breasts (in addition to an annual mammogram) include:
a.(MRI), once every two years or
b. ultrasound yearly or
c. tomosynthesis (3D mammogram) which may decrease recall rates and improve cancer detection rates.
Increased conspicuity of screen detected breast mass on tomosynthesis image (right) in comparison with 2D mammogram image (left).
Health care system capacity for this supplemental screening is an issue. MRI and ultrasound services are prioritized according to clinical urgency with people requiring diagnostic imaging taking priority, followed by screening for participants in the High Risk OBSP. And because women ages 40-49 can now self-refer for screening mammograms, and have on average higher breast density, we can expect increased volumes of BI-RADS D results.
In addition, only some sites have access to tomosynthesis. Currently tomosynthesis is being performed to screen category D breasts at Juravinski Hospital Breast Assessment Center, St Joes Hospital Hamilton, Joseph Brant Hospital in Burlington and Niagara Health sites, with more hospitals in our region to get this technology in 2025. Sometimes the mammogram technologists attempt to do perform a Tomosynthesis at time of screening appointment IF they recognize the patient as category D at the time of the mammogram. If a tomogram view is not done for category D breasts and the patient wants supplemental screening, primary care can refer to any of the sites offering tomosynthesis.
Those of us in primary care also need to know that our patients are notified by OH of their BI-RADS density score via their normal results letter from OH. Please see the sample letter for one year recall and for two year recall the letter includes a link to the Ontario Health webpage about breast (chest) density. So primary care will be asked about breast density and we need to know how to navigate our patients with BIRADS D density outside of OBSP.
I agree that these pathways are not well established yet. The OBSP does not include supplemental screening suggestions with ultrasound, MRI or tomosynthesis in its organized automatic follow up booking pathways. The mammogram report recommends a follow-up test in one year and does not suggest supplemental screening. Nor is supplemental screening health care system capacity established, nor uniform within our region. And at the same time, the patients know they are at increased risk via their results letter. This really puts the onus on primary care to discuss and navigate these higher risk patients with very dense breasts into supplemental tests that might have long wait lists or be declined. The OBSP program does intend to eventually include reporting and navigation that includes supplemental screening for BI-RADS D very dense breasts, but this will take time and require additional funding.
For now, patients with BI-RADS category D density breasts on their most recent mammogram will continue to be automatically invited by OBSP for their next mammogram in one year’s time. Primary care will need to decide, with their patients, if they want to refer for supplemental screening.
I would like to thank our regional OBSP lead, radiologist Dr. Meredith Lynch, for her contribution to this blog post. And remember, she is on econsult for any questions on specific patients. I know I have found her to be very helpful for my own patients.