Slower decrease in breast density associated with higher risk for developing breast cancer

In In The News by Barbara Jacoby

By: Drew Amorosi


Key findings:

  • Breast density decreased over time in both women who developed breast cancer and those who did not.
  • Women who developed breast cancer experienced a significantly slower decrease in breast density over time.

Declines in breast density occurred at a significantly slower rate among women subsequently diagnosed with breast cancer, results from a prospective longitudinal analysis study showed.

The findings, published in JAMA Oncology, suggest that incorporating longitudinal changes in breast density into existing models would allow for more personalized breast cancer risk management, the researchers noted.


Previous studies have suggested that breast density decreases among women as they age. Decreasing breast density also has been associated with cancer risk.

Colditz and colleagues wanted to know whether changes in mammographic breast density associated with aging differed from changes in density among women who eventually developed breast cancer.

“Because breast cancer does not develop in both breasts simultaneously, it is reasonable to use statistical approaches that evaluate each breast independently for changes in breast density and risk for breast cancer,” Colditz said.


Colditz and colleagues conducted a prospective nested case-control study to determine any association between changes in mammographic breast density over time and risk for developing breast cancer.

The study sample included 10,481 cancer-free women from the Joanne Knight Breast Health Cohort who received routine screening mammograms every 1 to 2 years from Nov. 3, 2008, to Oct. 31, 2020.

Investigators identified 289 women who developed confirmed breast cancer and matched each with about two control participants (n = 658) based on age and year at study enrollment. The final analysis included 947 participants (mean age, 56.7 ± 8.7 years; 80.6% white, 14.9% Black) and 8,710 craniocaudal-view mammograms.

A mean interval of 2 ± 1.5 years occurred between participants’ last mammogram and breast cancer diagnosis.

Longitudinal changes in participants’ volumetric breast density served as the study’s main outcome measurement.

Key findings

Investigators noted that breast density decreased over time for all women who participated in the study, including those who developed breast cancer and control participants.

However, when they analyzed density change in each breast separately, they found women who developed breast cancer experienced a significantly slower decrease in breast density over time compared with the decline seen among control participants (estimate = 0.027; 95% CI, 0.001-0.053).

Clinical implications

Accommodating for longitudinal tracking of breast density over time would not require additional resource utilization and should become part of standard breast cancer risk assessment for women who receive regular mammograms, according to Colditz.

“Digital mammograms make this type of breast density assessment possible, and digital mammograms are available at almost all screening locations these days,” he told Healio. “The changes needed to the process of screening and returning of results would not be complex to implement. It would simply mean updating approaches that many screening centers already have in place.”