Simple Blood Test Could Predict Outcomes for People With Advanced Breast Cancer

For some cancers, ctDNA can be used to make a diagnosis, see if cancer has come back, guide treatment decisions, and see how well a treatment is working.

How Well Did ctDNA Predict Prognosis for Advanced Breast Cancer?

This study, completed by scientists at the Institute of Cancer Research in London, analyzed liquid biopsies from 167 people participating in the plasmaMATCH clinical trial (NCT03182634). The participants had metastatic or locally advanced breast cancer and had received at least one prior treatment. To analyze the results, researchers looked at two groups of patients.

• Patients in group one had an identifiable mutation and were treated with targeted therapies.
• Patients in group two had triple-negative breast cancer (TNBC) and were treated with a combination of olaparib (Lynparza), a PARP inhibitor, and ceralasertib, an ATR kinase inhibitor being studied in clinical trials.

Baseline ctDNA, or the amount of ctDNA in the bloodstream before treatment began, was measured. It was then measured 4 weeks later.

When patients with TNBC had low levels of ctDNA before treatment began, they had a 67% lower chance of their cancer progressing. These patients also had a better overall response rate of 40%, compared to 9.7% for those who did not have a low baseline level of ctDNA. For patients with an identifiable mutation, the association between low baseline levels of ctDNA was not as strong.

After 4 weeks, lower levels of ctDNA was associated to better outcomes for patients with an identifiable mutation, but not patients with TNBC. No signs of ctDNA, or undetectable ctDNA, was associated with better outcomes in both groups.

 How Accessible Are ctDNA Tests Today?

While this study and others like it have shown how ctDNA can be used to help predict outcomes and guide treatment, liquid biopsies are currently not standard for advanced breast cancer, though some oncologists may use them in their clinics.

“Tests for ctDNA are accessible but unevenly available,” says Dr. Marleen Meyers, a medical oncologist at NYU Langone Health. “They may be costly and not necessarily covered by insurance, though coverage has expanded and may cover some indications.”

Dr. Meyers also cautioned that relying too much on liquid biopsies could have negative outcomes. “If ctDNA is negative, it may give false reassurance and tempt patients to de-escalate or stop treatment. CtDNA will likely have a role in the future, but more research is needed.”

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