Following my first mammogram, at 40, the physician reading my films (they weren’t digital back then) called me into her office. She looked very solemn and my heart started pounding as I waited to hear she had found something. “You have dense breasts,” she said. Then she stopped and just looked at me.
Relieved that I hadn’t heard that there was a lump, I exhaled and stared back, waiting for her to explain the significance of what she had just told me.
She explained that having dense breasts was a risk factor for getting breast cancer. She also stated that dense breasts were associated with a higher risk of death from breast cancer.
Two breast cancers later, I am relieved to hear that a new study found:
- High mammographic breast density is not associated with a higher risk of death from breast cancer.
- High mammographic breast density was not associated with risk of death from any cause after accounting for other patient and tumor characteristics.
- Mammographic breast density may be one of the strongest risk factors for developing breast cancer, but it doesn’t have an impact on survival.
In a national registry analysis by Gretchen L. Gierach, PhD, MPH, of the National Cancer Institute ( NCI), she and her colleagues found that high density had no correlation with risk of breast cancer death after adjustment for other factors. There was also no high density linked to all-cause mortality They reported their findings online in the Journal of the National Cancer Institute.
Researchers reported, “Risk factors for the development of breast cancer may not necessarily be the same as factors influencing the risk of death from breast cancer once it has developed. It is reassuring that elevated breast density, a prevalent and strong breast cancer risk factor, was not associated with risk of breast cancer death or death from any cause in this large, prospective study.”
The researchers examined 9,232 cases of primary invasive breast carcinoma diagnosed from 1996 through 2005 in the U.S. Breast Cancer Surveillance Consortium, an NCI supported population-based registry of breast imaging facilities.
During the mean follow-up of 6.6 years, 1,795 of the women died, 889 from breast cancer.
Breast cancer deaths, though, weren’t significantly more common in the higher-density classifications as ranked by the Breast Imaging Reporting and Data System (BI-RADS) overall in the model fully adjusted for site, age at diagnosis, year of diagnosis, cancer stage, body mass index, mode of detection, treatment, and income.
In the study, dense breasts weren’t linked to higher risk of death due to any cause. The only high breast cancer mortality-risk group appeared to be women with low-density breasts who were obese or had larger tumors of at least 2.0 cm, with significant hazard ratios.
Dr. Gierach’s group wrote, “Prior studies haven’t suggested these associations, but it’s plausible because breasts with a higher percentage of fat may contribute to a tumor micro-environment that facilitates cancer growth and progression. Breast density might be useful to integrate in clinical trials to see if it aids in identification of women most likely to benefit from targeted treatments or prevention strategies.”
The study was funded by the National Institutes of Health, the National Cancer Institute (NCI), and the NCI-funded Breast Cancer Surveillance Consortium.