ctDNA in Breast Cancer: Cancer Detection Vs Therapy Selection


A brief synopsis on the use of circulating tumor DNA for cancer detection versus treatment selection in breast cancer management.


Barry Rosen, MD:ctDNA [circulating tumor DNA] testing really falls into a much larger category of liquid biopsies, whether looking for circulating tumor DNA, or looking for circulating cancer cells or exomes. There are a number of tests that have been available for really over 2 decades looking at this. When you look at circulating tumor DNA, my medical oncology colleagues have been using this for a decade for targeting therapies, so that by identifying certain somatic mutations that are present in microscopic levels, they may actually target therapy. That has been around and has proven to be effective for a small subset of patients. What’s new about the circulating tumor DNA testing, especially as it pertains to the Signatera test, is that that’s a personalized test designed using the patient’s tissue from their breast cancer, where we could then design a unique test, which has a much higher sensitivity and specificity. That test, I think will be very effective as we’re looking at a systemic surveillance.

Another area for circulating tumor DNA testing is in the screening realm, and I think this is a very exciting area right now, looking at far more cancers than just breast cancer. We’re fortunate that we do have a relatively good screening tests for breast cancer; mammograms and supplemental tests, such as ultrasound and MRI, will find many cancers. But there are many cancers where we don’t have screening tests, and perhaps circulating tumor DNA will bridge that gap and allow us to do more effective screening for other cancers. Now, as it pertains to breast cancer, while I think our screening methods are good, we know that we miss cancers. We know that women with dense breasts, for example, if a woman has a screening mammogram and has dense breast tissue, there’s a 25% to 50% chance we won’t see their cancer by mammography. Now, perhaps ctDNA…and it’s wonderfully complementary to imaging, so by combining the 2, I would anticipate that the ability to screen for breast cancer should definitely improve. Likewise, for personalized screening for younger women for whom we know mammograms aren’t as effective, perhaps by incorporating ctDNA screening, this will give us a better chance of really looking at the highest-risk population and trying to do more precision prevention and early detection.

Transcript edited for clarity.

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