The chances for a woman to receive mammogram result as "denser breast" may depend on how the radiologists read the mammogram, says a new study.
Denser breasts are a risk factor for breast cancer because tumors are harder to spot in dense breast tissue.
"Part of the message is that the assessment of dense breasts is subjective," said lead author Brian Sprague of the Office of Health Promotion Research at the University of Vermont in Burlington.
‘Dense breasts make it harder for radiologists to detect possible abnormalities on a mammogram, which could be a risk factor for breast cancer.’
Dense breasts are one factor for decision-making about breast cancer screening, but not the only factor, added Sprague.
For the study, researchers analyzed more than 200,000 mammograms performed on 145,000 women ages 40 to 89 between 2011 and 2013. Eighty-three radiologists from 30 radiology facilities evaluated the mammograms.
The radiologists rated each breast as 'almost entirely fat,' 'scattered densities,' 'heterogeneously dense' (some non-dense tissue but most of the tissue is dense) and 'extremely dense.'
Heterogeneously dense and extremely dense are the two categories that qualify as "dense" based on state legislation.
About 37% of the mammograms were rated as showing dense breasts. However, the distribution of the four categories varied widely by a radiologist. The authors noted that some radiologists have rated as few as 7% as dense, while others rated 85% as dense.
Age at first period, age at the birth of first child, having a first-degree relative with breast cancer and a history of prior benign disease all influence breast cancer risk as well.
"The paper highlights the disconnect between density laws and breast density measurement, it was never intended to be something that really dictated screening decisions," said Sprague.
Most of the radiology centers use computer models to interpret breast density in mammograms which may allow a more objective rating. Women with dense breasts should seek digital mammography which improves detection of cancers.