Photo Credit: Panuwat
Dr. Marla Lipsyc-Sharf reviews her recent session at the 2024 SABCS meeting, discussing biopsy approaches and treatment sequencing in metastatic breast cancer.
In a session at the 2024 San Antonio Breast Cancer Symposium, Marla Lipsyc-Sharf, MD, and co-presenters discussed a case series and reviewed considerations for clinicians conducting biopsies and selecting treatments in patients with metastatic, ER+ breast cancer.
Physician’s Weekly (PW) spoke with Dr. Lipsyc-Sharf to gain insight into key takeaways from the session.
PW: What are the main takeaways from your presentation?
Dr. Lipsyc-Sharf: There are several takeaways from the panel. In the cases that I’ll be presenting, we are looking at when to do tumor biopsy versus liquid biopsy, which is a blood test for circulating tumor DNA or other nucleic acid analytes. Another case focuses on when to move on from endocrine-based therapies and which chemotherapies or antibody-drug conjugates should be considered first after estrogen-targeted therapies.
Can you go into more detail about the biopsy approach?
We are fortunate that in the United States, many people can access testing on both the patient’s tumor and on circulating tumor DNA, which are fractions of DNA that have been shed by tumor cells into the blood. There are some pros and cons to each approach.
Tissue sampling, which has been the gold standard historically, is the best way to confirm receptor status. For example, how estrogen receptor-positive or progesterone receptor-positive a tumor is, whether they have HER2 overexpression—that can be evaluated with a tissue biopsy and is not routinely done on liquid biopsy or circulating tumor DNA.
On the flipside, a circulating tumor DNA sample can pick up on genomic alterations or mutations from different metastatic sites that have been released into the blood.
When you do a tissue biopsy, you only test for mutations at that site. If you are doing a biopsy to confirm receptor status or the cost of the liquid biopsy is prohibitive, then you want to go with the tissue biopsy.
However, if time is of the essence, you need a quick answer, and you’re looking at alterations that could change treatment in someone with multiple metastatic sites, then you might want to pursue a liquid biopsy. Similarly, if it’s unsafe to pursue a tissue biopsy—if the tissue is in a precarious location that’s not accessible with a needle—that’s another good time to pursue a liquid biopsy.
Can you also elaborate on considerations for sequencing therapies in these patients?
Yes, absolutely. Many recent studies are calling into question how we sequence our targeted therapies: whether we should be administering targeted therapies in the first line setting or the second-line setting, as is most traditional for this kind of breast cancer. Also, when patients move from endocrine therapy to chemotherapy versus antibody-drug conjugates, we consider which antibody-drug conjugate to use versus chemotherapy.
For example, when it is time for patients to move from endocrine-based therapy to chemotherapy, many clinicians and patients discuss whether to pursue trastuzumab deruxtecan, which is an intravenous treatment, or an oral chemotherapy such as capecitabine. Often, it’s a conversation with patients where we discuss the advantages and disadvantages of each therapy.
Sometimes, there’s a clear medical answer. For example, if someone has reduced lung function, we would not want to pursue a treatment like trastuzumab deruxtecan, which can lead to pneumonitis, which is very rare but can be serious. Alternatively, we have a lot of patients who try to avoid alopecia for as long as possible. Those patients often will choose to pursue oral chemotherapy like capecitabine rather than go right to an intravenous chemotherapy, which imparts a higher risk for hair loss.
