“Tumors — breast cancers in general — are intimately associated with the blood vessels,” explained Dr. W. Fraser Symmans.
The detection of fragments of cancer cells or cancer DNA in the bloodstream may offer patients with breast cancer and their providers prognostic and treatment-related insights, explained Dr. W. Fraser Symmans.
Symmans, who is a professor of pathology and translational molecular pathology at The University of Texas MD Anderson Cancer Center, recently provided an overview of circulating tumor DNA (ctDNA) and circulating tumor cells (CTC) in breast cancer at the CURE® Educated Patient® Breast Cancer Summit.
“Tumors — breast cancers in general — are intimately associated with the blood vessels,” he said during his presentation. “So, it stands to reason that if cells die, which they regularly do, because of the whole growth process, or if there are areas where the entire regions of the tumor dies in response to treatment, bits of them — or sometimes all of the cells — find themselves in the bloodstream.”
Both CTC and ctDNA are “convenient ways to get a sample,” according to Symmans, who said that both are done via blood draw, which is less invasive than obtaining a biopsy of the tumor.
The technology for CTC was developed before that of ctDNA, and this method usually tests blood for a specific target, such as the HER2 protein found in HER2-positive breast cancers, explained Symmans. But now, ctDNA testing is becoming “the dominating approach,” as experts can now test for a whole panel of known breast cancer-associated mutations, or even from the patient’s own tumor.
ctDNA is currently being used in other malignancies, such as lung cancer, to predict prognosis and guide therapy.
READ MORE: ctDNA May Help Predict Lung Cancer Outcomes, Guide Treatment
“You get a representative sample of what might be happening anywhere in the body,” Symmans said.
Symmans explained, however, that patients and doctors must also consider other factors when predicting which patients may be at a higher risk for experiencing relapse for patients with early-stage breast cancer. He emphasized that there is a need for negative predictive value (NPV) — which is the probability that a patient with a negative ctDNA test won’t develop a recurrence — for each subset and stage of early-stage breast cancer.
Additionally, Symmans said that there is a need for better and more accurate modeling of the timing for future risk of recurrence, that takes into account stage and subtype, prognostic and predictive test results, measurable responses to prior treatments and comprehensive risk profiling. These, all together, will hopefully all be combined to paint a broader picture of a patient’s disease and how to best treat it.
“There is no question in my mind, that this is an important contribution to understanding risk, but it is by no means the only contribution. The other contributions are not overlapping — they’re independent. They’re adding together to give the whole profile,” he said. “So I think our real future is understanding the staging information and the prognostic biology and the blood monitoring and the timing and understanding that if you have this type of breast cancer and have a PCR, the timing and risk can be mapped out.”
Symmans said that we’re still “a ways away from that,” but he remains optimistic.
“This is going to be with us for a very long time as we work out all the kinks and as we optimize it. It’s a new tool, it has some very strong characteristics, but we don’t have all of the answers yet,” Symmans concluded. “But we will be able to, in time, make this tool to be part of a precise monitoring program for the early breast cancer setting.”
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