Decreased breast density over time means decreased breast cancer risk

Washington, Apr 21 (ANI): A decrease in breast density, depicted via the proportion of fibroglandular tissue on the mammogram image, over time indicates a decreased risk of breast cancer, according to a study.

Researchers from the Mayo Clinic campus in Minnesota found a 28 percent reduced risk of developing breast cancer in women whose breasts decreased in density, as seen from two different mammograms taken an average of six years apart, compared to women whose breast density did not change.

Dr. Celine Vachon, study's lead investigator, said that two measures of breast density may, therefore, provide additional information for assessing breast cancer risk.

However, she added that this information is not ready for use in clinical practice to inform breast cancer risk.

"Replication of these findings in other studies will be important. Also, improved and standardized measurements of breast density are needed for the assessment of changes in density," she said.

The current assessment available in most clinical settings is BI-RADS, Breast Imaging-Reporting and Data System, which is relatively unsophisticated when it comes to measuring breast density and was not intended for this purpose, said Vachon.

"There is a lot of ongoing work aimed at improving measures of density, so that situation should change," she added.

This study was drawn from the Mammography Health Study, which enrolled 19,924 women who were free of breast cancer, had screening mammograms performed at Mayo Clinic between 2003 and 2006 and resided in Minnesota, Iowa and Wisconsin.

From this large group, the researchers selected participants who had at least one additional screening mammogram prior to enrolment, and then looked at clinic and tumour registries in the three Midwestern states to determine if any of these women developed breast cancer after enrolling in the study.

Measures of mammographic density were obtained from the two mammograms, an average of six years apart, for the approximately 1,900 women randomly sampled from the cohort, and from all 219 individuals who were diagnosed with breast cancer during follow-up.

The researchers found that women who developed breast cancer were less likely to experience a decrease in density in a second mammogram.

After adjusting for other potential factors contributing to breast cancer development, the researchers found that women who decreased one BI-RADS category or more over an average of six years were at 28 percent reduced risk of developing breast cancer, compared to women whose density was unchanged.

"We know that breast density can change with time, as evidenced by decreases seen with women going through menopause or using the breast cancer preventive drug tamoxifen and increases seen with postmenopausal hormone therapy use. Our results suggest that decreases in density may translate to decreased breast cancer risk," said Vachon.

The study was presented at the American Association for Cancer Research (AACR) 101st Annual Meeting 2010. (ANI)