A family history of breast cancer (FHBC) is positively associated with mammographic breast density in premenopausal women, according to a study published online Feb. 17 in JAMA Network Open.

Yunan Han, MD, from the Washington University School of Medicine in St. Louis, and colleagues examined the association of FHBC and mammographic breast density in premenopausal women. The analysis included a discovery set of 375 premenopausal women and a validation set of 14,040 premenopausal women.

The researchers found that discovery set participants who had FHBC were more likely to have a higher mean volumetric per cent density versus participants with no FHBC (11.1 versus 9.0%). In an adjusted analysis, volumetric per cent density was higher in women with FHBC compared with women without FHBC (odds ratio [OR], 1.25; 95% confidence interval [CI], 1.12 to 1.41) and in women who had one affected relative (OR, 1.24; 95% CI, 1.10 to 1.40).

However, volumetric per cent density was not significantly higher in women who had at least two affected relatives (OR, 1.40; 95% CI, 0.95 to 2.07) versus women with no relatives affected. In the validation set, findings were similar, with women with a positive FHBC more likely to have dense breasts (BI-RADS 3-4: OR, 1.30; 95% CI, 1.17 to 1.45) versus women without FHBC; the odds of having dense breasts were also higher in women with one affected relative (OR, 1.29; 95% CI, 1.14 to 1.45) but not significantly higher in women with at least two affected relatives (OR, 1.38; 95% CI, 0.85 to 2.23) versus women with no relatives affected.

"The findings highlight the heritable component of mammographic breast density and underscore the need to begin annual screening early in premenopausal women with a family history of breast cancer," the authors write.