Since the 1960’s, mammography has proven to be an invaluable tool in screening for breast cancer, spotting the disease before women show any symptoms.
Now, a new large-scale study shows that a 3-D screening method called digital breast tomosynthesis (DBT) is significantly better at detecting the potentially fatal disease. It’s also less painful than mammography — the breast doesn’t have to be compressed as much — and exposes women to less radiation.
The research was published online on May 1, 2015 in the journal European Radiology.
“Our study is unique since it is the only population-based trial that investigates breast tomosynthesis alone compared to mammography, and our first results are really striking,” Dr. Sophia Zackrisson, a radiologist at Lund University in Sweden and one of the study’s authors, says in a video describing the research (above).
Flat versus 3D
For the study, the researchers recruited 7,500 women between the ages of 40 and 74 and screened them for breast cancer using both traditional mammography and DBT.
Whereas traditional mammography produces one flat image of the breast — which can obscure tumors — DBT takes X-ray images from multiple angles, which are then used to produce 3-D images throughout the entire breast.
Together, the screening methods detected breast cancer in 68 women. Twenty-one of those cases were identified only by DBT, while one of the cases was identified only by mammography. Overall, DBT found more than 40 percent more breast tumors compared to mammography.
One downside was that the DBT yielded a higher recall rate, meaning more cancer-free women had to be called in for additional tests. That’s a bit surprising, as previous research found DBT to have lower recall rates.
All screening techniques present the risk for over-diagnosis — mammography, for example, has a false-positive rate of 10-20 percent. This can result in unnecessary psychological distress and intrusive procedures such as biopsies, the researchers note, so minimizing the occurrence of false-positives is an important goal for any new screening technique. The researchers do not know what that number is for DBT, and they have called for further studies to investigate the issue.
What’s the takeaway?
DBT is not yet the standard of care for breast screening, but the researchers say that may soon change. “We see a change as inevitable. Breast tomosynthesis will be introduced, it is just a question of when and on what scale,” Dr. Zackrisson said in a statement.
Currently, DBT is available alongside other screening techniques at many U.S. hospitals, though the cost remains a barrier — the 3-D imaging is more expensive than mammography and, depending a woman’s insurance, may or may not be covered. That’s something the researchers hope to address in ongoing research.
A five-year study is underway to determine who may benefit the most from DBT. Until then, women should discuss with their physicians whether or not they are an ideal candidate for the scan.
Experts believe women with dense breast tissue and women who may have scar tissue from breast surgery or biopsies can benefit most from the accuracy of DBT. Mammography has typically performed worse and shown lower accuracy for women who have dense breast tissue (or scar tissue), which can make it harder for doctors to see cancer on a mammogram.
DBT may also provide a new screening option for young women with high breast cancer risk. For example, women who are carriers of the BRCA genetic mutation were previously recommended to begin yearly digital mammograms between ages 25-30, since this mutation puts them at much higher risk of getting breast cancer. However, newer studies have found that starting yearly mammograms before age 35 has no benefit and may instead be harmful due to the radiation exposure. If proven effective, DBT could give young women with a BRCA mutation a new, safe way to assess their breast health.
Though DBT has not been widely adopted, the researchers are optimistic about the progress of ongoing trials and say 3-D breast imaging could be incorporated into routine screening over the next decade.
“We see five to ten years from now as a possible timeframe for the large-scale introduction of the technique. There is also an aspiration for more personalized screening, and breast tomosynthesis could therefore be one of several methods used,” said Dr. Zackrisson.
Breast cancer remains the most common cancer in women, and the second deadliest, according to the CDC. The American Cancer Society estimates that around 40,290 women in the U.S. will die from breast cancer in 2015.