A new study led by researchers at the UBC faculty of medicine has revealed that ultrasound screening significantly improves breast cancer detection in women with dense breasts—identifying twice as many cancers as previously estimated.
The study, which evaluated more than 5,200 women in British Columbia with dense breast tissue (categories c and d), found that supplemental ultrasound screening following a normal mammogram led to the detection of 32 breast cancers. The majority of these were early-stage invasive cancers that had not yet spread to the lymph nodes.
The findings were recently published in the Canadian Association of Radiologists Journal.
“This can not only save lives—detecting breast cancer earlier also improves quality of life for these women, reducing the need for more aggressive surgeries and chemotherapy,” said lead author Dr. Paula Gordon, clinical professor of radiology at UBC’s faculty of medicine
The study reported a high incremental cancer detection rate (ICDR) of 6.1 per 1,000 screens, highlighting how ultrasound can detect cancers in dense breast tissue that would otherwise be missed by standard mammography.
The researchers say the findings are critical for Canadian breast cancer screening policies, where 2D mammograms remain the standard and screening is most often conducted every other year.
Despite the benefits of supplemental ultrasound screening, most provinces and territories in Canada do not offer publicly funded supplemental screening for women with dense breasts. British Columbia is one of the few provinces that does, and has provided publicly funded supplemental ultrasound for women with category c and d dense breasts since 2019.
“The limited access to supplemental screening means many women are at increased risk of later-stage cancer diagnoses,” said Dr. Gordon.
Additional technologies, such as MRI, are considered even more sensitive for detecting breast cancer in dense breasts, but they are costly and have limited availability. While MRI is sometimes offered to women with category d breast density or those with a high lifetime risk, the study found that the vast majority of cancers detected—84 per cent—were in women with category c breast density, and 62 per cent had no personal or family history of breast cancer.
The researchers hope their findings will inform national screening policies and push for greater equity in early detection of breast cancer across Canada.
“We have the technology to detect breast cancer earlier and improve outcomes for women with dense breasts. What we need now is policy change to ensure that all Canadian women with dense breasts—regardless of where they live—have access to the screening tools they need. Every woman deserves an equal opportunity for early detection,” said Dr. Gordon.
Approximately 43 per cent of women have dense breasts, meaning their breasts are made up of less fatty tissue and more glandular and fibrous tissue.
While having dense breasts is normal, it puts women at higher risk of developing breast cancer. It also makes it harder for radiologists to detect cancer.
“On a mammogram, both cancers and normal dense breast tissue appear white. It’s like trying to see a snowball in a snowstorm,” said Dr. Gordon. “For this reason, mammograms are not enough for women with dense breasts, which is why it’s important that we inform women of their breast density and provide supplemental screening.”
Ultrasound uses sound waves to create detailed images of breast tissue, allowing radiologists to detect abnormalities in dense breast tissue that may be hidden on a mammogram.
However, the researchers say a major challenge is that many women are unaware of their breast density. Breast density is classified into four categories — a, b, c and d — with categories c and d being considered dense breasts. The only way to determine where a woman fits on the scale is through a mammogram.