Integrating ctDNA Into Breast Cancer Management: Joanne Mortimer, MD, FACP, FASCO

At a recent Institute for Value-Based Medicine^® event, Joanne Mortimer, MD, FACP, FASCO, medical oncologist at City of Hope in Los Angeles, California, shared her insights on the evolving role of circulating tumor DNA (ctDNA) in breast cancer management. Mortimer discussed how ctDNA testing is being applied in real-world practice, from identifying actionable mutations such as PIK3CA, ESR1, PALB2, and BRCA to monitoring patients with difficult to assess disease. Mortimer also reflected on challenges in patient communication around ctDNA, payer coverage for genomic testing, and unique barriers faced by men with breast cancer.

This transcript was lightly edited; captions were auto-generated.

Transcript

With increasing attention to the integration of genomics in breast cancer, how do you approach the use of ctDNA in real-world practice, particularly in terms of timing, actionability, and choosing among available assays?

Most of the ctDNA results for which we have actionable treatments are in the hormone-positive patients. Increasingly, we use ctDNA to look at somatic mutations in patients whose disease has progressed on a previous line of endocrine therapy. The actionable options there are looking at PIK3CA mutations, ESR1 mutations, or even somatic mutations in PALB2 or BRCA, which provide another opportunity for systemic therapy in those women potentially.

Other uses of ctDNA to look for tumor that's residual tumor, I think is less well defined. Certainly, there are women that I use ctDNA to follow their cancer, specifically patients who have bone-only disease. It is often hard to tell if patients are responding to therapy or not. In theory, ctDNA goes up, presumably their disease is progressing, if there's some question about the CT or the PET scan. It doesn't take the place of a conventional staging, but I think it provides another piece of information along with the patient's symptoms, to help you make decisions about whether you need to change therapy or continue on the current treatment.

How do you help patients understand the implications of biomarker testing results, particularly when findings are uncertain or provoke anxiety?

I think the ctDNA being used to monitor patients’ cancer status, whether they have recurrence or remission, is probably the hardest to explain or justify right now, because we really don't have enough data to know for sure that elevations in ctDNA in somebody who's an adjuvant patient is evidence of recurrent disease. I don't use it in that setting. Patients love the idea that that might be useful, but I try to discourage them from using ctDNA for just those purposes.

For purposes of changing therapy, most patients are pretty savvy about the importance of looking at their tumor DNA and that their own individual cancer and what their own cancers mutations are that will help you to define new targeted therapies. It's not a difficult concept. I think most people grasp that pretty quickly.

How do you approach the sequencing of high-cost targeted therapies when multiple options are available, and how does payer coverage impact that process?

In the state of California, you cannot tell a person what tests they can or cannot order. I think for most institutions around the country, most certainly most cancer centers, we have our own platforms for looking at genomic changes in cancer. We have not had significant problems getting payer coverage for these sorts of tests. We do use our own platform.

What are some of the challenges related to testing in male patients with breast cancer?

When you order these tests, they are never covered by insurance, because there's no data for them in men. The reality of treating men with breast cancer is that we treat them exactly like we treat women. There's probably no reason to think that these genomic tests and ctDNA are any different than how they should be used than they are in women. Nonetheless, payers will not pay for it.