Joyce A. O’Shaughnessy, MD: Hello, and thank you for joining this OncLive^® Peer Exchange^® titled “Emerging Concepts in Treating Triple-Negative Breast Cancer.” Triple-negative breast cancers are vastly heterogeneous tumors, as you know, and they remain very clinically challenging to us with outcomes that are far surpassed by other breast cancer subtypes. But treatment approaches are rapidly evolving and we’re gaining further insight into the biologic rationale for more personalized approaches and the potential for immunotherapy. In this OncLive^® Peer Exchange^® panel discussion, my colleagues and I will discuss recent progress surrounding the identification of triple-negative breast cancer subgroups, promising novel approaches to treatment, and refinement of chemotherapy use.

I am Dr. Joyce O’Shaughnessy. I’m the Celebrating Women’s Chair in Breast Cancer Research at Baylor University Medical Center in Texas Oncology and chair of the US Oncology Breast Cancer Program in Dallas, Texas. And joining me as our distinguished panel today: Dr. Aditya Bardia, attending physician at Massachusetts General Hospital Cancer Center, assistant professor at Harvard Medical School, and director of Precision Medicine at the Center for Breast Cancer in Boston, Massachusetts. Hi, Aditya.

We have Dr. Claudine Isaacs who is professor of medicine and oncology and co-director of Breast Cancer program at the Lombardi Cancer Center and at MedStar Georgetown University Hospital in Washington, DC. Hi, Claudine. And Dr. Tiffany Traina, clinical director of Breast Medicine Service and associate attending at Memorial Sloan Kettering Cancer Center, and associate professor of medicine at the Weill Cornell College of Medicine in New York City. So, thank you very much for joining us. It’s going to be a great discussion.

We’re going to talk about new data, but we’re also going to try to keep it as practical and practice-focused as possible because that’s where we really need the help. We’re going to start off by talking a little bit about triple-negative breast cancer subgrouping. Is there anything that’s helpful to us? Aditya, how do you conceptualize triple-negative these days?

Aditya Bardia, MD, MPH: Yes, if we think about triple-negative breast cancer, it is defined by what it does not have rather than what it has. And we can look at the classification of triple-negative breast cancer, it came about because of ER and HER2. So, previously, we had breast cancer, then we had ER and tamoxifen, and that really developed the classification of ER-positive and ER-negative disease. And then we had HER2 and trastuzumab, and that essentially led to triple-negative. But we don’t define triple-negative by what it has, and so there has been interest in molecular classification. PAM50 probably is the one that is mostly used. And based on PAM50, you can divide breast cancer, in general, to luminal A, luminal B, HER2-enriched, and basal-like. But one thing to consider is that some of the triple-negative breast cancers based on the clinical classification could even be luminal A or luminal B. And while the majority of triple-negative breast cancers are basal-like, there is a decent overlap with the clinical and the molecular classification. So, the bottom line is, does it influence our clinical management? At this time, we don’t have specific therapies that are linked to say basal subtype of breast cancer, and that’s why this molecular classification is not used in clinical practice. If we have a specific clinical trial with a particular molecular subtype, then we would consider molecular classification or even genotyping. But outside of that, I think it’s a good research tool but we don’t use it in clinical practice.

Joyce A. O’Shaughnessy, MD: It’s really not a reason to get EGFR staining or cytokeratin-56 at this time, really because, though that does delineate a basal subset, we’re not going to really do anything with that today in practice.

Transcript Edited for Clarity