Dense Breast Tissue May Possibly Be Linked to Increased Rate of Cancer for Women

Dense Breast Tissue May Possibly Be Linked to Increased Rate of Cancer for Women

Edited by:  Fern Sidman  

Scientists have long known that dense breast tissue is linked to an increased risk of breast cancer in women. According to a recent report in the New York Times, a study published last Thursday in JAMA Oncology reveals that that while breast density declines with age, a slower rate of decline in one breast often precedes a cancer diagnosis in that breast.

Scientists at Washington University in St. Louis analyzed breast density changes over a 10-year period in 10,000 women who were free of cancer when the study started, the NYT reported. Some 289 women were diagnosed with breast cancer in that time; the study compared changes in their breast tissue to those in 658 similar women who did not develop breast cancer.

The NYT reported that breast density was higher from the start in the women who went on to develop breast cancer, and density declined in all women over time. But when each breast’s density was measured separately, scientists found a significantly slower decline in density in breasts that developed cancer, when compared with the other breast in the same patient.

CNN reported in January 2023 that the study, published in JAMA Network Open, surveyed 1,858 women ages 40 to 76 years from 2019 to 2020 who reported having recently undergone mammography, had no history of breast cancer and had heard of breast density.

Women were asked to compare the risk of breast density to five other breast cancer risk factors such as having a first-degree relative with breast cancer, being overweight or obese, drinking more than one alcoholic beverage per day, never having children and having a prior breast biopsy.

“When compared to other known and perhaps more well-known breast cancer risks, women did not perceive breast density as significant of a risk,” said Laura Beidler, an author of the study and researcher at the Dartmouth Institute for Health Policy and Clinical Practice, as was reported by CNN.

Dense breasts tissue refers to breasts that are composed of more glandular and fibrous tissue than fatty tissue. It is a normal and common finding present in about half of women undergoing mammograms, the report stated.

Breast density changes over a woman’s lifetime, and is generally higher in women who are younger, have a lower body weight, are pregnant or breastfeeding, or are taking hormone replacement therapy, CNN reported. The level of breast cancer risk increases with the degree of breast density; however, experts aren’t certain why this is true.

The American Cancer Society reported that having dense breast tissue is common. Some women have more dense breast tissue than others. For most women, breasts become less dense with age. But in some women, there’s little change.

Dr. Harold Burstein, a breast oncologist at the Dana-Farber Cancer Institute who was not involved in the study told CNN that, “One hypothesis has been that women who have more dense breast tissue also have higher, greater levels of estrogen, circulating estrogen, which contributes to both the breast density and to the risk of developing breast cancer.”  He added that, “Another hypothesis is that there’s something about the tissue itself, making it more dense, that somehow predisposes to the development of breast cancer. We don’t really know which one explains the observation.”

The NYT reported that Shu Jiang, the study’s lead author and an associate professor of public health sciences at Washington University, said the findings might provide an individualized and dynamic tool for assessing a woman’s breast cancer risk. “I hope they can get this into clinical use as soon as possible — it will make a huge difference,” she said.

“Right now, everybody only looks at density at one point in time,” Dr. Jiang added, according to the NYT report. But women have mammograms at regular intervals throughout their lives, and the density of each breast is measured each time.

“So this information is actually already available, but it’s not being utilized,” she said. Now, a woman’s risk of developing breast cancer could “be updated every time she gets a new mammogram.”

The NYT also reported that dozens of states have started requiring mammography centers to notify women if they have dense breast tissue. In March, the Food and Drug Administration recommended that providers tell women about their breast density.

But this is the first study to measure changes in density over time and to report a link to breast cancer, according to the NYT report.