Breast density crucial cancer indicator says study
The density of breast tissue is second only to age as an indicator of breast cancer risk, according to the largest ever study of the issue to date.
The link between breast density and breast cancer risk has been known about for some time, but the report is one of the first to compare the link to other risk factors.
The study drew on screening data taken from more than one million women, identifying 11,638 who went on to get cancer within the following year.
This was then compared against further clinical information in an attempt to identify risk factors.
After adjusting for age, women with dense breast tissue were almost four times more likely to be at risk of cancer than those with the least dense breasts.
Additionally, the results showed that the link was due to the breast density itself, rather than simply because it is harder to detect tumours in mammograms of denser breasts.
"Although breast cancer is harder to detect in women with dense breasts, our research showed that women with dense breasts are more likely to develop breast cancer," said lead author Dr William Barlow.
The researchers cautioned that not enough is known about the phenomenon to produce an accurate risk analysis using the findings, however.
Stephen Duffy, Cancer Research UK Professor of Cancer Screening, said: "This study confirms previous findings that breast density is a key risk factor for breast cancer and demonstrates that density has an effect on risk independently of other risk factors. "Bearing in mind that density affects large numbers of women and that it is alterable by lifestye or hormone suppression, it is clearly going to be of practical use in identifying high risk groups for preventive measures or increased monitoring.
"Whether a reduction in an individual woman's breast density is automatically followed by a reduction in her risk of future breast cancer, however, is a crucial question for future research." The study was conducted by members of the Breast Cancer Surveillance Consortium in the US and is published in the Journal of the National Cancer Institute.