A recent study from the University of Eastern Finland concluded that very low mammographic breast density significantly worsens breast cancer‘s prognosis. The authors show that disease free survival and the general life expectancy were much shorter in women who had very low breast density when compared to those with high density breasts.

The observations support the observation that reduced density of breast tissue corresponds to lower amounts of fibroglandular tissue versus fat tissue. These findings might prove significant in the evaluation of breast cancer treatment approaches and prognosis.

In this study, 270 patients (between 32 and 86 years of age) with breast cancer registered at the Kuopio University Hospital were studied. The density of breast tissue was analyzed through mammographic images obtained when diagnosis was revealed. Researchers calculated the amount and proportion of dense glandular tissue within the total breast area. The density of breast tissue was divided in two categories: low (when the proportion of glandular tissue was under 25 percent) and very low (when the proportion of glandular tissue was under 10 percent).

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The study consisted of a 6-year follow up focusing on the effects and consequences of different breast tissue densities and additional mammographic features that could influence breast cancer prognosis.

The outcomes revealed that very low breast tissue density is, in fact, an independent poor prognostic factor for breast cancer, despite patient’s age, body mass index or menopausal status. About 70.7 percent and 87.7 percent of women with very low breast tissue density and higher proportion of glandular tissue, respectively, were alive after the 6 years of follow-up. Further, lower breast tissue density was linked to to more aggressive breast tumors.

These are particularly interesting outcomes considering dense breast tissue has long been associated with a higher risks of cancer. “It is difficult to detect small tumours when screening dense breasts, and this results in a higher occurrence of clinically detectable interval cancers. In the U.S., it is nowadays mandatory to let patients know if they have dense breast tissue. This allows them to choose whether they wish to have further tests, for example a screening ultrasound,” said study author Dr. Ritva Vanninen, in the press release. “It could be assumed that dense breast tissue would also be associated with a poorer prognosis in patients with a recently diagnosed breast cancer. However, this was not the case in our study, as low breast tissue density specifically weakened the prognosis,” she added.