Women with dense breasts more likely to get breast cancer in both breasts
Breast cancer patients with dense breasts are twice as likely to develop cancer in the other breast, according to new research.
The study, published in the journal Cancer, is one of the first to describe the association between breast density and the risk of cancer in the non-cancerous or contralateral breast.
The author, Associate Professor Dr Isabelle Bedrosian, says the study highlights the challenges in managing treatment for women with dense breasts, in particular the consideration of bilateral mastectomy or removal of both breasts.
Dr Bedrosian from the University of Texas Anderson Cancer Center says the 10-year risk for contralateral breast cancer is as low as 2 percent in certain patients, but is as high as 40 percent in other patient subsets. The wide range depends on the risk factors affecting each patient.
“We know there are a number of well-established influences for developing both primary and secondary breast cancers, such as BRCA gene mutations, family history, and the tumour’s estrogen receptor status,” she says.
“We also know density is a risk factor for the development of primary breast cancer. However, no one has closely looked at it as a risk factor for developing contralateral disease.”
The team examined the records of around 680 patients treated at the Anderson Cancer Center between 1997 and 2012. Women with BRCA mutations were excluded from the analysis because they are at higher risk for contralateral breast cancer.
Researchers divided the patients into 229 who had developed contralateral breast cancer and 451 who had not.
They assessed which patients in each group had dense breasts, based on mammogram readings and categorisations from the American College of Radiology. Dense breasts are those with a high level of breast and connective tissue, compared with fat.
Only 51.7 percent of those who did not have contralateral breast cancer had dense breasts at diagnosis, while nearly 61 percent of those had cancer in both breasts were deemed to have dense breasts.
After adjusting for other breast cancer risk factors, researchers concluded that patients with dense breasts were twice as likely to develop contralateral breast cancer than women with non-dense breasts.
“Our findings have valuable implications for both newly diagnosed patients with dense breasts and for breast cancer survivors as we manage their long-term risk of a secondary diagnosis,” says Dr Carlos Barcenas, an assistant professor of breast medical oncology at the Anderson center.
Chair of the Breast Cancer Aotearoa Coalition, Libby Burgess, says research about breast density and the risks associated with denser breasts is growing.
“It’s important for women to be aware of how dense their breasts are so that they can make informed decisions about screening and treatment,” she says.