In women with BRCA mutations, increased mammographic breast density is not associated with a higher risk of breast cancer and should not be a factor in making decisions about treatment, Canadian researchers report.
Increased mammographic breast density is a known breast cancer risk factor in the general population but it was not known whether that would hold true in women with BRCA1 or BRCA2 mutations.
Kavitha Passaperuma of the University of Toronto, Canada, and her associates studied the relationship between mammographic breast density and subsequent risk of breast cancer in 462 women (mean age, 44 years) with BRCA1 or BRCA2 mutations who were enrolled in a screening program for high-risk women (J Clin Oncol. 2010:28:3779-3783). A single, blinded observer measured quantitative percentage density (PD) on each participant’s baseline mammogram using a computer-aided technique.
A total of 50 cancers were diagnosed during the study period, 38 invasive and 12 ductal carcinoma in situ. Mean PD was not significantly different in the 376 women who did not develop breast cancer than in the 46 with cancer, 34% and 31%, respectively. Results remained nonsignificant on multivariate analysis and when women with pure DCIS were excluded.
“Lack of correlation between mammographic breast density and breast cancer risk is an important finding,” the authors write, “because it suggests that breast density should not be considered a factor when counseling women with BRCA mutations who are making decisions about prophylactic surgery or chemoprevention.” These women, they say, are unlikely to benefit from prevention strategies aimed specifically at reducing breast density.