About 1 in 8 women in the US will develop invasive breast cancer during their lifetime, according to the American Cancer Society. For decades, mammography screening has been used to diagnose women given the large medical consensus that it reduces breast cancer mortality. Criticism of 2D mammography has grown over time, though, especially because of the number of false positives. Dr. Julianne Greenberg, Director of Breast Imaging for Washington Radiology Associates is the co-author of two large studies published in 2014 in The American Journal of Roentgenology (AJR) and The Journal of the American Medical Association (JAMA), which show that 3D mammography—technically known as breast tomosynthesis— finds significantly more invasive cancers and reduces unnecessary recalls.
MedicalExpo e-magazine: When was 3D mammography invented?
Julianne Greenberg: 3D mammography has been in development for close to 20 years. However, it was approved in the United States for clinical use by the Food and Drug Administration in 2011. It is an up and coming technology and I am pretty confident that in a relatively short period of time it will become a standard of care like 2D mammography is today.
The majority of the mammography machines are not 3D mammography yet, but the transition process with a new technology always takes a little bit of time.
ME e-mag: Can you explain how this technology can increase cancer detection and reduce recall rates?
Julianne Greenberg: We achieved these results because of the nature of 3D mammography, which addresses some problems that are inherent in 2D mammography. One of those problems that produces a higher recall rate for 2D mammography is that tissues in the breast tend to get overlapped and this can cause a finding or a questionable lesion on an initial screening mammogram, which then requires the patient to be recalled for additional imaging. 3D mammography has the advantage of being able to look at very thin slices of tissue, as if you were looking through a pack of cards, so you can see what is in your hand. Now you can look at each individual card, see in those thin slices what is a normal breast tissue and what could be a potential true suspicious lesion. So that’s how it reduces the recall rates.
The other advantage is that overlapping tissues on a 2D mammogram can obscure a true breast cancer, so being able to see these slices of tissue on 3D images and analyzing them will allow us to uncover or reveal a significant lesion that might have been missed otherwise in 2D mammograms. That is why you see in these studies that there is an increased cancer detection rate with tomosynthesis.
In both the JAMA and AJR studies, we reduced the recall rate by 16% and the overall cancer detection rate was increased by 29% compared to 2D mammography. But even more important than that, the invasive cancer detection rate was increased by 44%. The invasive breast cancers are the ones that can kill women, so that is really significant.
ME e-mag: Is 3D mammography more painful or more expensive than 2D mammography?
Julianne Greenberg: From patient’s point of view, it is exactly the same exam they have always had. There are two versions of 3D mammography. With the newest one, patients are in compression for the same amount of time as 2D mammography, and with the other one they are in compression for a few seconds longer, but it is a very minor issue.
There are also slight differences in the radiation dose but they are very minimum; you have to remember that mammography itself is an extremely low-dose exam. With the newest version of 3D mammography, the dose differences are minuscule.
Regarding the price, in the U.S. Medicare is now paying for 3D exams as well as many of the insurance companies that are coming on board. It will take a while for that trend to continue and become more universal in the country, but it is certainly on the way.
ME e-mag: Does 3D mammography make radiologists more confident in their diagnoses?
Julianne Greenberg: Absolutely. We feel much more confident, especially in telling patients, ‘Hey, I read your screening mammogram and it looks fine and negative. I don’t see anything of concern.’ There are about 50% of women who have dense breasts and saying those words with such confidence is much more difficult when you are reading a 2D mammogram, because you know that, especially for women with dense breasts, the issue of overlapping tissues obscuring significant cancers is always in the back of your mind.
So 3D mammography has been a great relief. We feel much more confident about our diagnoses, our ability to tell patients that we are confident their mammogram is negative and our ability to identify suspicious lesions.
[An example of next-generation mammography :”True 3D” breast tomosynthesis as announced by Siemens during RSNA]
ME e-mag: Do you think that 3D mammography could silence criticism about mammography in general?
Julianne Greenberg: One of the big advantages of 3D is its ability to get even higher cancer detection rates than 2D mammography, but also to bring down the recall rates. This is very significant for women because it is a very difficult moment when you are recalled for a second mammogram. It creates anxiety, it takes time, it is expensive.
The JAMA study included more than 454,000 patients. This is an extremely large clinical trial. The scientific analyses are very sound and it is very difficult to argue with those kinds of numbers. By demonstrating with such studies that you have this type of data, it will help silence those critics of mammography.