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Black women demonstrate denser breast tissue than white women
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PHILADELPHIA — Black women exhibited significantly higher breast density than white women in an association that was not explained by BMI and cancer risk factors, according to study results presented at the American Association for Cancer Research Annual Meeting.
“Breast density is a strong risk factor for breast cancer,” Anne Marie McCarthy, PhD, a research fellow at Massachusetts General Hospital, told HemOnc Today. “The literature has been mixed as to whether black women have similar levels of breast density, or higher or lower levels of breast density than white women. The point of our study was to compare levels of breast density for black and white women using quantitative breast density measures from a computer algorithm.”
Racial variances in BMI might have contributed to the lower breast density observed among black women in previous studies, according to study background.
McCarthy and colleagues evaluated data from 2,845 black and white women (mean age, 57 years) with no previous history of breast cancer. All the women had their BMI recorded at the time of mammography screening.
The mean age was comparable in both cohorts; however, black women demonstrated a significantly higher mean BMI compared with white women (32 kg/m2 vs. 26 kg/m2; P < .001).
Researchers used a software algorithm developed at their institution to evaluate absolute and percent area density per women, as well as an FDA-approved software (Quantra, Hologic, Inc.) to calculate volumetric estimates of absolute and percent dense tissue.
Overall, black women had significantly higher absolute breast area (40.1 cm2 vs. 33.1 cm2; P < .001) and volume (187.2 cm3 vs. 181.6 cm3; P < .001) compared with white women. However, white women displayed a higher area (23.5% vs. 19.6%; P < .001) and volume percent density (13.4% vs. 11.6%; P < .001).
When researchers adjusted for age, BMI and cancer risk factors, black women demonstrated a significantly higher breast density in all categories, including absolute area density (P ˂ .001) area percent density (P = .021), absolute volume density (P ˂ .001) and volume percent density (P ˂ .001).
“This might have implications for breast cancer risk or prognosis,” McCarthy said.
Researchers observed a significant association between race and BMI for area percent (P = .001) and volume percent density (P < .001) and nearly significant associations for volume density (P = .085). Density was more frequently linked to BMI in white women across all three measures.
“Our next step will be to see how quantitative density measures and other imaging biomarkers are associated with cancer risk, cancer subtype and stage of diagnosis by race,” McCarthy said. “We also want to look at larger populations.” – by Cameron Kelsall
Reference:
McCarthy AM, et al. Abstract 6580. Presented at: American Association for Cancer Research Annual Meeting; April 18-22, 2015; Philadelphia.
For more information:
Anne Marie McCarthy, PhD, can be reached at Massachusetts General Hospital, 9th Floor, 50 Staniford St., Boston, MA 02114; e-mail: ammcarthy8@partners.org.
Disclosure: The researchers report no relevant financial disclosures.
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Chi-Chen Hong, PhD
Mammographic density is one of the strongest risk factors for breast cancer, but most studies to date have been conducted among white women with very limited data available in black women. McCarthy and colleagues examined race differences in breast density in one of the largest studies to date — composed of 1,589 black and 1,256 white women — and showed that black women had higher levels of absolute density, but lower levels of percent density after adjustments for age, adiposity and breast cancer risk factors. Given these differences, it will be important in future studies to determine the specific measure of mammographic density that best predicts breast cancer risk among black women, who have lower overall breast cancer risk compared to white women. In addition, greater understanding of the relationship between breast density and adiposity is particularly important among black women since they are more likely to be overweight or obese. Interestingly, compared to Caucasians, mammographic density levels among black women in the study were less likely to be associated with adiposity, suggesting that the underlying mechanistic pathways supporting the development of mammographic dense breasts may differ between black and white women. Differences in breast density levels between white and black women also were not explained by differences in breast cancer risk factors. In future studies, it will be interesting to determine if breast density levels are associated with greater African ancestry. Findings from this study are an important step in generating greater understanding of how mammographic density impacts breast cancer risk among black women.
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