How does breast density compare to other risk factors for developing invasive breast cancer?

The charts below detail relative risk and prevalence [1-6].

Relative Risk: The top chart shows approximate relative risk of developing invasive breast cancer by age 80 for a woman with a given risk factor compared to a woman without that risk factor: 1) disease-causing BRCA1 or -2 mutation; 2) prior ductal carcinoma in situ; 3) prior atypical ductal hyperplasia; 4) first-degree relative (mother or sister) diagnosed with breast cancer by age 50; 5) combined estrogen and progesterone therapy after menopause; 6) heterogeneously dense breast tissue (relative to a woman with fatty breasts); or 7) extremely dense breast tissue (relative to a woman with fatty breasts).

*The 15-year risk of developing invasive breast cancer among women with untreated DCIS (i.e. found on retrospective review of surgical biopsy specimens years later) is about 10 times greater than the risk in the general population [4, 5]. The risk 3 years or more after DCIS diagnosis in women who receive standard treatment is nearly 3 times greater than the risk in the general population [6].

Prevalence: The lower chart shows estimated prevalence of each risk factor in American women aged 40-74, except for hormone replacement therapy which applies only to postmenopausal women. Dense breast tissue is quite common, seen in 43% of all women aged 40-74.