Breast tomosynthesis, commonly called 3D mammography, is a relatively new imaging technique that catches more breast cancers than regular 2D mammograms while more accurately identifying harmless spots as benign.
Recent research reveals how well it works…
- A study from Norway included 12,631 women who were screened with both 2D and 3D mammography. When radiologists had access to both the 2D and 3D exams, they detected 40% more cases of invasive breast cancer the type that has spread outside the milk duct or lobule and into the breast tissue itself) than when they saw only the 2D exams.
- In a separate study from Massachusetts General Hospital, the combination of 2D and 3D mammography reduced false-positive results (when a suspicious-looking abnormality is found but turns out to be benign) by 39%.
Diane LoRusso, MD, a clinical assistant professor at Weill Cornell Medical College who has practiced radiology for nearly four decades, calls 3D mammography a "remarkable breakthrough and a major improvement in our ability to detect breast cancer."
But: There are some downsides to the 3D test. Should you be asking your doctor for a 3D mammogram? Here's the info you need to decide…
The Benefits Of 3D
A regular mammogram is a two-dimensional picture of a three-dimensional object that's been flattened out by those uncomfortable breastsquishing plates. Because the compressed breast tissue ends up overlapping itself, one feature can hide in the shadow of another, making it difficult to find tiny cancers hidden in the breast. (Imagine a bunch of letters of the alphabet being layered one on top of the other. They'd be hard to read, right? That's similar to what happens with a 2D mammogram image.)
For the 3D mammogram, the breast is still compressed between the plates—but the arm of the X-ray machine rotates in an arc above the breast, taking 15 separate images. Those are then processed on a computer to create a 3D image that the radiologist can manipulate to view 50 to 60 individual millimeter-thin slices" of breast tissue. By eliminating overlapping structures, abnormalities are more easily seen. (Imagine that pile of alphabet letters being separated layer by layer. You could view each letter individually, so they would be easy to read.)
The 3D images help radiologists pin down the size, shape and precise location of abnormalities-details that tend to be obscured on 2D images. The improved visibility explains why 3D mammograms detect tumors that 2D mammograms miss...and why the new technology is less likely to yield those anxiety-producing false-positive results that lead to unnecessary (and expensive) extra testing.
Currently, 3D mammography is used in addition to regular mammography, not instead of it-so even if you opt for the 3D test, you'll still need regular 2D mammograms as well. One reason is that an important aspect of mammogram reading is to compare a patient's new images with her previous images to see whether anything has changed. Since those previous images were all 2D, for comparison's sake, you need a 2D version of your current images, too. Fortunately, both scans can be performed on the same mammography equipment in rapid succession. (In May 2013, the FDA approved the use of a low-dose 3D mammography alone (the software is manufactured by Hologic, Inc.)—but separate 2D tests are still the norm.)
Radiation is another concern. Though the 3D scan uses about the same amount of radiation as the 2D scan, combining the two doubles your radiation exposure. Still, the total radiation dose for the combined test is well below three milligray, which is the FDA limit for a single mammogram-and it's less than the radiation dose from the film (rather than digital) 2D mammograms of the past. As Dr. LoRusso pointed out, because 3D mammograms produce fewer falsepositive results, your overall radiation dose may be lower in the long run since you're less likely to be called back for additional mammograms.
The amount of breast compression involved in 3D mammography is no different from that required for a 2D scan. However, to do both the 2D and 3D tests, you have to endure that breast squishing a bit longer-for about six to 12 seconds per breast, compared with the two to four seconds needed for just the 2D test alone.
The good news: The design of the compression device on the 3D unit is more comfortable for most patients, Dr. LoRusso said.
Another downside is the expense. Insurance companies generally do not cover 3D mammography because they still consider it experimental. Hopefully, this will change in the not-to-distant future and it certainly couldn't hurt to ask your insurance company to cover your 3D test). For now, though, you'll probably have to pay the extra cost yourself. Typically this ranges from about $50 to $100, depending on your location and your doctor-a small price to pay for improved cancer detection.
Making Your Choice
Dr. LoRusso recommends the 3D test for all her mammography patients because research shows that it benefits women with all breast types.
However, it is particularly important for the 30% of women whose breasts are dense (meaning that they contain more glandular or connective tissue than fatty tissue). Mammogram X-rays do not see through dense tissue as easily as they see through fat tissue-cancerous tissue and dense areas both appear white on the mammogram, so identifying cancer is like trying to pick out a particular cloud in a cloud-filled sky.
Ask your local radiology center or hospital whether it provides 3D mammography...or use the manufacturer's locator service. Currently about 300 radiology centers in the US offer this test. To learn more about 3D mammography and see the machine in action, check out this video from Dr. LoRusso's Web site at www.rye radiology.com/3d-digital-mammography.
Finally, Dr. LoRusso said, it is very important to realize that 3D mammography should not replace other breast tests that your doctor may recommend. For instance, if you have dense breasts or palpable masses, you also may need breast ultrasound screening...if you are at very high risk for breast cancer due to genetic factors, you also may need a breast MRI. In short, 3D mammography is an important new tool in the fight to detect breast cancer, but it is not the only tool.