By Liam Davenport, medwireNews Reporter
Although high-density breast cancer high breast density on mammography is an established risk factor for developing breast cancer, it is not associated with an increased risk for death, say US investigators who suggest different factors may affect risk at different times.
The team, led by Gretchen Gierach, from the National Cancer Institute, in Rockville, Maryland, notes: "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."
They add in the Journal of the National Cancer Institute: "Our findings underscore the need for an improved understanding of the biological characteristics of and the relationships between the breast tissue components that are responsible for the inter-individual variations in breast density."
Examining data on 9232 women from the US Breast Cancer Surveillance Consortium diagnosed with primary invasive breast carcinoma between 1996 and 2005, the researchers found that 84% of women were diagnosed with Breast Imaging Reporting and Data System (BI-RADS) density categories 2 or 3.
Women with BI-RADS 1 or 2 density tended to be younger, premenopausal, leaner, residents of higher income areas, current users of menopausal hormone therapy, and nulliparous or older at first birth than those with BI-RADS 3 or 4 density.
The team analyzed 60,759 person-years of follow up and 1795 deaths, of which 889 were from breast cancer, 810 from other causes, and 96 of uncertain cause. On multivariate analysis, high-density breast tissue was not related to the risk for death from breast cancer or from all causes, at nonsignificant hazard ratios of 0.92 and 0.83, respectively, after adjusting for site, age at and year of diagnosis, American Joint Committee on Cancer stage, body mass index, mode of detection, treatment, and income.
Looking at the results by stage and other prognostic factors led to similar results, aside from a significant increase in breast cancer death in women with low-density breasts who were obese or had tumors at least 2.0 cm in size, at respective hazard ratios of 2.02 and 1.55.
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