observed during mammography, according to a new study of two retrospective cohorts published online Feb. 17 in JAMA Network Open. The findings suggest that breast density measured during mammography may have a genetic component, and suggest the importance of initiating early mammography in premenopausal women with a family history of breast cancer.
“We know that mammographic breast density is a very strong risk factor for breast cancer, probably one of the strongest risk factors, and it’s also a surrogate marker for breast cancer development, especially in premenopausal women. We also know that family history of breast cancer is a strong risk factor for breast cancer as well. Surprisingly, we have very limited information on how these risk factors are related to each other. There have been only two studies that have been done in this field in premenopausal women, and the studies are conflicting. So, we felt that we need to really understand how these two factors are related to each other and whether that would have an impact on modifying or refining mammographic screening in high-risk women,” Adetunji T. Toriola, MD, PhD, MPH, said in an interview. Dr. Toriola is professor of surgery at Washington University, St. Louis.
Previous research identified risk factors for dense breast tissue. A genome-wide association study found 31 genetic loci associated with dense breast tissue, and 17 had a known association with breast cancer risk.
In the JAMA Network Open study, the researchers included data from women who were treated at Washington University’s Joanne Knight Breast Health Center and Siteman Cancer Center. The discovery group included 375 premenopausal women who received annual mammography screening in 2016 and had dense volume and non-dense volume measured during each screen. The validation set drew from 14,040 premenopausal women seen at the centers between 2010 and 2015.
In the discovery group, women with a family history of breast cancer had greater volumetric percent density (odds ratio [OR], 1.25; P < .001). The validation set produced a similar result (OR, 1.30; 95% confidence interval, 1.17-1.45). Subanalyses revealed similar associations in non-Hispanic White and Black or African American women.
The current study included a higher percentage of women with a family history of breast cancer than previous studies, and also controlled for more variables. This may have removed confounding variables that could have affected previous studies.
“It reinforces the need to start mammogram screening early in women who have a family history of breast cancer,” Dr. Toriola said.
The study had some limitations, including a higher percentage of women with a family history of breast cancer than the National Health Interview Survey (23.2% and 15.3%, versus 8.4%), explained by the fact that women with a family history of breast cancer are more likely to seek out screening. The average age of women was on average 47 years, making them closer to perimenopausal than premenopausal.
The study was funded by the National Institutes of Health.