A new study in the journal Cancer says that women who have been treated for breast cancer have a higher chance of recurrence if they have “dense” breast tissue. And in fact, those with the densest tissue are four times more likely to relapse than those with less dense tissue, the study says.
The research suggest that treatment might be changed for those in the densest group to include radiation, but that those in the less dense group may not need it. More studies are needed before anything would happen, however.
The researchers, from Women’s College Hospital in Toronto, Canada, studied medical records and mammograms of 335 women who had lumpectomies for invasive breast cancer tumors. They categorized the women’s breasts as low, intermediate or high density (using the accepted Wolfe scale, which categorizes breasts with less than 25% dense tissue as low, 25-50% dense tissue as intermediate, and more than 50% dense tissue as high).
Over 10 years, the women in the highest density group had a 21% risk of breast cancer recurrence, vs. a 5% risk for those in the low density group.
Among those who did not have radiation in addition to surgery, the rate of recurrence went up to 40% in women with the highest density breasts.
The researchers are not sure why the densest tissue has the higher rate of recurrence. Several factors may be a part of it: younger women generally have dense breast tissue, and also more often have estrogen-fed cancers. Tumors may be harder to find in dense breast tissue, thereby becoming larger before being discovered.
"One reason for this could be that we know breast density increases the risk of a breast cancer in the first place, so it may simply increase the risk of a second one,” Stephen Duffy, Cancer Research UK's professor of screening, told BBC News. "Another possibility is that the dense tissue makes it more likely that other areas of cancer in the breast are not visible at initial diagnosis and so are not removed when surgery takes place.
This isn’t the first time that the issue of dense breast tissue and its place as a breast cancer indicator has been studied. In 2007, another study found that cancer occurs five times more often in women with extremely dense breasts than in those with less dense breasts. That article suggested that the role of tissue density in the breasts was a higher risk factor than was being acknowledged.
“It’s been ignored to an absolutely unbelievable degree,” said Dr. Norman Boyd, the research leader of that study at Princess Margaret Hospital in Toronto.
His team studied how and when cancers were discovered over 8 years in the records of 1,112 women collected between 1981 and 2006.It was published in the New England Journal of Medicine.
From an Associated Press article about that research:
“In this study, women with at least 75 percent dense breasts showed five times more likelihood of cancer than women with less than 10 percent density.
“The researchers went further by calculating just how many more cancers were found at screening, within the next year, and in the years afterward. Cancers found within a year were considered likely to be present, but masked, during the earlier mammogram. But a true biological risk was seen in cancers discovered by mammogram or long afterward.”
Density of more than 50 percent accounted for 16 percent of all cancers and 25 percent in women under age 56.
This link takes you to an about.com article that has a slideshow of mammography images. There are six images. The first two show you the difference between a mammogram where the breast has a lot of fatty tissue (less density), and the second shows a breast with less fat tissue (more density):
What does this mean to you, as a woman and/or as a breast cancer patient?
First of all, start becoming aware of your own breast density. When your doctor reviews your mammogram with you, ask about how your breast density would be classified. Should you ever be diagnosed with cancer, it may be good information to have when you are questioning your doctors about possible treatment. And in future studies researching breast tissue density, you’ll have a frame of reference.
Second, if you do have very dense breast tissue, it is even more crucial that you are dedicated to self-exams and mammograms. Getting used to how your own breasts feel over time make you more likely to find a change. And having a series of mammograms over the years gives doctors a baseline for you.
Here’s today’s story, from Healthday news on EmpowHer:
The BBC report:
The Los Angeles Times report:
The Associated Press on the 2007 study:
The journal Cancer (must be registered):
Does this report bring up more questions in your mind? Please let us know. We'll do our best to research and answer them, and if we can't find the answers on our own, we can ask one of the members of our Medical Board to give us her or his opinion.