Posted: Nov 20, 2012 6:33 PM
Nov. 20, 2012 -- Although mammograms remain the gold standard for breast cancer screening, they are not the perfect test.
They don't find up to 30% of cancers, and they often find something that may be suspicious for cancer but really isn't after additional testing. These are called false-positive results.
Some researchers are seeing better results by adding another form of testing, called three-dimensional or 3-D breast imaging.
"This technology makes a big impact," says researcher Elizabeth A. Rafferty, MD, a radiologist and director of breast imaging at Massachusetts General Hospital in Boston.
"Three-dimensional mammography addresses the two major flaws of mammography," she says. One is the inability to see some cancers on a mammogram. The other is a need to call back women for what looks like abnormal tissue that isn't, she says.
The study is published in the journal Radiology. Hologic, the maker of the 3-D system studied, funded the study as part of the process to receive FDA approval for the test, Rafferty says. She does not work for Hologic.
The FDA approved the 3-D system in early 2011. It is now installed in more than 300 centers, according to Jim Culley, a spokesman for Hologic.
Rafferty says using 3-D is helpful for routine screening and for high-risk women.
A conventional digital mammogram is only two-dimensional. It produces a single, flattened image.
The 3-D system captures multiple images from different angles around the breast. It helps give the radiologist clearer views through overlapping breast tissue.
A woman having both types is not likely to notice any difference, as both digital and 3-D mammograms can be done on the same equipment.
Women in the study received mammograms at five different sites between July 2006 and May 2007. Of the 997 women eligible, complete analysis was done on 622.
Each had a digital mammogram and a 3-D mammogram.
The rate at which cancer was correctly identified increased by up to 16% by adding the use of 3-D. That means ''as many as 16% more cancers will be found," Rafferty says.
The impact of the 3-D mammogram on diagnosing cancer in dense breasts, she says, has been even better in her other research. "Women with dense breasts are at higher risk and their cancers are more difficult to find," she says.
The rate of false-positive recalls for more testing declined by nearly 40%.
At Massachusetts General, the 3-D mammograms are done at no additional charge, Rafferty says. Other institutions may charge $30 to $50 extra, Culley says. Sometimes insurance covers the bill, he says.
One of the study authors is an employee of Hologic and another is a statistical consultant. The researchers who do not have industry conflict, including Rafferty, had control of the data and report for the journal.
Although the study is well done, there is still work to be done on 3-D mammograms before they can be called a game-changer, says Debra Monticciolo, MD. She is chair of the American College of Radiology's Quality and Safety Commission, and president of the Society of Breast Imaging. She reviewed the findings for WebMD.
One drawback, she says, is that women who get both tests are exposed to more radiation. "Each of their patients got twice the dose," she says of their study participants, ''even though the combined dose is less than the FDA [acceptable] limits."
"I think it is going to be one of those things that will help us," says Monticciolo, vice chair of research at Scott & White Health Care in Temple, Texas. "But we still need more data."
Eventually, Rafferty says, it will be possible to have only the 3-D test, reducing the total radiation dose.
That is possible, Culley says, because of a new process by which the computer can create a synthesized 2-D image from the 3-D, without actually doing the 2-D mammogram. Then, the radiologist can review both images while reducing the radiation exposure.