Screening for Dense Breasts

Equity for women with dense breasts

New Brunswick should offer supplemental screening for women with dense breasts.

Women with dense breasts are discriminated against if they can only have mammograms for breast cancer screening. They deserve equity for early detection to women with non-dense breasts to both decrease mortality and to give them less aggressive treatment options.

Many more cancers could be detected early, and lives saved, if women with dense breasts were offered supplemental screening.

Dense breast tissue makes it harder to see cancer on a mammogram and increases the risk of getting breast cancer. Women with dense breasts are more likely to be diagnosed with larger and more aggressive cancers, and have a poorer prognosis.

Benefits of ultrasound for women with dense breasts

Ultrasound can detect a small cancer in an early stage before it spreads to lymph nodes.

In women with dense breasts, studies show that for every 1000 women screened, ultrasound finds another 2-3 cancers that were not seen on mammogram.

Several large studies have shown that supplementing mammograms with ultrasound can increase detection up to 97% in women with dense breasts.

It has been known since 1995 with a Canadian study that ultrasound finds significant numbers of additional cancers missed on mammograms. That study spurred more research, all showing the benefit of ultrasound. In 2022, a study published by Vancouver authors showed they found 7 additional cancers per thousand women using supplemental screening ultrasound exams. All cancers have been small and node negative. Significantly, 40% were in women with no family history and 60% were in women with Category C density.

Preliminary findings from Japan’s J-START RCT show a reduction in interval cancers by half. It would be unethical to wait for J-START to show mortality reduction, since reduced interval cancers precede mortality reduction.

This comprehensive article on dense breasts and supplemental screening outlines the risks of dense breast tissue, and the current and future modalities that can detect cancers missed on mammograms.

Annual screening with mammography leads to fewer interval cancer cases: A Canadian study showed that annual screening with mammography for women with Category D density leads to fewer interval cancer cases.

Other jurisdictions
  • Although no screening program offers supplemental screening, screening ultrasound is accessible in BC and Alberta, and covered by provincial health insurance.
  • PEI has committed to ultrasound for women with Category D.
  • In other provinces, access can vary depending on the physician.
  • As well, six provinces offer annual screening with mammography to women in Category D. New Brunswick does not invite women with Category D density to return annually.
  • Based on new RCT data from the Netherlands, the European Society of Breast Imaging now recommends MRI every 2 to 4 years for all women in category D. Yet, in New Brunswick, screening ultrasound is not even easily accessible for women with dense breasts.

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