Very low mammographic breast density worsens a woman's breast cancer prognosis, according to a recent study published online in European Radiology.
Finnish researchers found that disease-free survival and overall life expectancy were significantly shorter in women with very low-density breast tissue compared to women with high-density breast tissue (Eur Rad, March 4, 2015).
Lead author Dr. Amro Masarwah, of the University of Eastern Finland in Kuopio, and colleagues included 270 breast cancer patients between the ages of 32 and 86 in the study, which spanned six years of follow-up. The group analyzed breast tissue density based on mammographic images at time of diagnosis, categorizing tissue density as low when the proportion of glandular tissue was below 25%, and as very low when the proportion was below 10%.
The researchers found that very low breast tissue density is an independent factor for poor prognosis from breast cancer, regardless of patient age, menopausal status, or body mass index. Of women with very low breast tissue density, 70.7% were alive at the end of the six-year follow-up, while 87.7% of women whose proportion of glandular tissue was higher than 10% were alive at the end of the same period. Lower breast tissue density was also associated with more aggressive higher-grade tumors, Masarwah's group discovered.
The findings are surprising because dense breast tissue is known to be associated with increased cancer risk, co-author Dr. Ritva Vanninen said in a statement released by the University of Eastern Finland.
"It could be assumed that dense breast tissue would also be associated with a poorer prognosis in patients with a recently diagnosed breast cancer," Vanninen said. "However, this was not the case in our study, as low breast tissue density specifically weakened the prognosis."