Among the flood of questions raised by the recent uproar over mammography screening guidelines is this one: Are there other breast imaging methods that can do a better job of detecting cancers needing treatment in women under 50—and not detecting things that don't?
Dr. Carol Lee
We asked Dr. Carol Lee of Memorial Sloan-Kettering Cancer Center in New York City. She chairs the American College of Radiology's commission on breast imaging.
Here's an edited version of our conversation.
How can we distinguish cancers that are going to cause problems from the ones that aren't?
Clearly, clearly, we need somehow to figure out which cancers are potentially deadly and which ones aren't. This is a matter of tumor biology. But until we get that sorted out, we can't say we're going to stop looking for cancers.
Are there imaging technologies available now to help sort this out?
There are other ways to image the breasts — ultrasound, MRI, some nuclear medicine techniques — but none has been shown to decrease mortality from breast cancer. So really, there is nothing that is suitable for replacing mammography. Here we have a test that we know works, that the US Preventive Services Task Force acknowledges to decrease mortality. But in their equation, the risks or the harms do not justify the benefits among most women aged 40 to 49. That's where we disagree.
When you say none of the other tests have been shown to reduce breast cancer mortality, is that because mammography has been studied so much more? Or are you saying that the newer tests are not likely to do any better?
The former. They're newer. We haven't done hundreds of thousands of women with many, many years of follow-up in a controlled setting the way the mammography trials have been done. Ultrasound and MRI will detect cancers not seen on mammograms. There's some usefulness there. But in no circumstance are they meant to replace mammography. They've been studied as an adjunct to mammography, mainly in high-risk women. We know we can find more cancers by using these tests. But we don't know whether it will affect mortality, or in whom to use them. There's a lot of uncertainty. These are not mature tests the way mammography is.
How do you currently decide when a woman might need one of these adjunctive tests?
There are guidelines. Women who have the BRCA1 or BRCA2 gene. Women who have a very strong family history. Women who have been treated with chest irradiation between the ages of 10 and 30. In these women, adding supplemental MRI to mammography has been shown to pick up cancers that would otherwise go undetected. In terms of ultrasound, there was recently a study looking at ultrasound in women at increased risk of breast cancer who also had dense breast tissue. It found that ultrasound can be useful in those women in addition to mammography in picking up cancers that would otherwise not be picked up. But the numbers of cancers you pick up in the general population using these other tests has not been studied at all because they're reserved for high-risk women or special circumstances. The number of false positives associated with ultrasound or MRI are relatively high.
At this point, nobody in the field imagines that these other technologies are likely to supplant mammography?
That's absolutely correct.
And is anything else coming along to try to do a better job?
Well, there's something called tomosynthesis. It gives you a sort of a three-dimensional view. You take a series of 10 to 12 images and the computer reconstructs the images. You can scroll through the tissue of the breast. It's not FDA-approved yet. The hope is that because you don't have a lot of overlapping normal tissue obscuring abnormalities you might be able to pick up cancers better. But that has yet to be shown. And I think that's what's holding up FDA approval. Tomosynthesis may or may not pan out.
What can you say about digital mammography that a lot of radiologists are using these days instead of the older machines that use x-ray film?
Digital mammography may prove to be more effective. There was a large study, the DMIST trial, that showed the sensitivity of digital mammography was higher in younger women and premenopausal women. So it may turn out that digital mammography has a greater mortality reduction that film screening does. It may be something that even the Preventive Services Task Force would recommend using routinely for women in their 40s. But it hasn't been studied extensively enough to make that recommendation.
So is there any technology that's going to come to the rescue here?