Giving Compass' Take:

• Katherine Hobson reports that breast density is both a risk factor for cancer and an impediment to effective screenings, but there is little to do about it. 

• How can funders help to increase awareness about this risk factor? What further research is needed on this subject? 

• Learn how to find and fund scientific research. 

In most states, when a woman gets the results of a mammogram, she also by law receives information about breast density. That’s the degree to which a woman’s breasts are made up of ducts, glands and connective tissue versus fatty tissue. And density matters — it’s a risk factor for breast cancer and it makes cancer harder to detect.

It’s clear that mammograms are a less effective screening tool for women with dense breasts, but what’s not clear is what women with dense breasts should do. The U.S. Preventive Services Task Force’s current recommendations say there’s not enough information to know whether offering these women additional screening will help them, and so many women are being given potentially concerning news without any proven ways to address it. The legislators, in other words, have gotten ahead of the scientists, who are still grappling with how to advise women with dense breasts.

Density is a spectrum, not a binary measure. Radiologists have classified it into four categories, with almost entirely fatty breasts on one end, and extremely dense breasts at the other. When physicians talk about “dense breasts,” they mean the top two categories, which include about 43 percent of U.S. women between the ages of 40 and 74. That makes it a very common risk factor, affecting tens of millions of women. To complicate things, density classifications depend on a radiologist’s reading and judgment calls, so they’re not necessarily consistent over time or between practitioners. And density can change over a woman’s life span; dense breasts are more common among younger women, for example.

Read the full article about breast density as a cancer risk by Katherine Hobson at FiveThirtyEight.