As we have previously reported, “dense breasts” refers to breasts that are composed of a greater proportion of fibrous and glandular tissue compared to fatty tissue. The density can only be determined from a mammogram and cannot be felt by a woman during breast self-examination (seen right). Since dense breast tissue poses up to four times higher risk of developing breast cancer, it is important for women to know their own density status. In the USA, there is a proliferation of mandated written notifications about breast density following a routine mammogram, and yet there appears to be little understanding of the risk.
Researchers from Dartmouth College in New Hampshire set out with the objective to assess women’s perceptions of breast density compared with other breast cancer risks and to explore their understanding of risk reduction. The group’s findings have just been published in JAMA Network Open and the article is freely accessible by clicking here. The authors surveyed 1858 women, aged 40 to 76, who had recently undergone a mammography examination and had no history of breast cancer. All had heard of breast density.
The survey was designed to explore whether the women understood the relative risk of breast density compared to other well known risk factors, such as family history, being overweight or obese, drinking more than one alcoholic beverage per day, never having children, and having had a prior breast biopsy. As seen at left (© JAMA), 93% of the women saw family history as having the greatest risk, when in fact fewer than 15% of breast cancers are of genetic origin.
As seen below right (© JAMA), more than 50% believed that a prior biopsy posed a greater risk for breast cancer than dense breast tissue. A subset of 61 women participated in a telephone interview and only six identified breast density as a contributing factor to breast cancer risk. Interestingly, most of them correctly recognised that breast density could make mammograms harder to read.
While digital breast tomosynthesis (DBT) is fast replacing mammography in the USA, it can still fail to detect tumours in dense tissue and that is why follow-up imaging with ultrasound is advocated. Given that almost half of all women aged 40 and above have either heterogeneously dense or extremely dense breasts, it is obviously a concern that many women – and indeed their doctors – do not fully appreciate the risk posed by dense breast tissue. That is why the authors concluded, “Comprehensive education about breast cancer risks and prevention strategies is needed.”