Best Practices for Molecular Testing in Early-Stage Breast Cancer

Expert panelists share their perspectives on best practices for molecular profiling in patients diagnosed with early-stage breast cancer.

Aditya Bardia, MD, MPH:
Hello, and welcome to this OncLive® Peer Exchange® titled “Data-Driven Decision-making in Advanced Breast Cancer.” I’m Aditya Bardia, a breast medical oncologist at Massachusetts General Hospital and Harvard Medical School [in Boston, Massachusetts]. I’m looking forward to the discussion. Joining me are 4 of my colleagues. Sara?

Sara A. Hurvitz, MD: Hi there, Aditya. I’m happy to be here. I’m Sara Hurvitz from UCLA [the University of California, Los Angeles].

Aditya Bardia, MD, MPH: Virginia?

Virginia Kaklamani, MD: Hi, everybody, my name is Virginia Kaklamani. I’m a medical oncologist at UT [the University of Texas] Health [Science Center at] San Antonio.

Aditya Bardia, MD, MPH: Heather?

Heather McArthur, MD: Hello, I’m Heather McArthur. I’m the clinical director of breast oncology at UT Southwestern [Medical Center] in Dallas, Texas. It’s great to be with all of you.

Aditya Bardia, MD, MPH: Michelle?

S. Michelle Shiller, DO, AP/CP, MGP: Hello, Aditya and team. It’s great to be with you all for this OncLive® discussion. My name is Michelle Shiller, and I’m a molecular pathologist with Baylor [Scott & White Health] in Dallas, Texas. I’m part of PathGroup at a national level. I look forward to the discussion.

Aditya Bardia, MD, MPH: Fantastic. Thank you for joining us. Let’s get going on our first topic. Let’s start with Michelle. You want to review biomarker testing in early breast cancer. What do you typically recommend for testing for a patient with early stage breast cancer? ER [estrogen receptor], PR [progesterone receptor], HER2 [human epidermal growth factor receptor 2], or other things?

S. Michelle Shiller, DO, AP/CP, MGP: At our institution, for early stage breast cancer, we test for hormone receptor status through estrogen receptor and progesterone receptor testing by immunohistochemistry [IHC]. HER2 expression in invasive disease, followed by FISH [fluorescence in situ hybridization]. For the proliferative index we also look at Ki-67 by IHC.

Aditya Bardia, MD, MPH: What’s the methodology for these tests? Is it all IHC based? Do you use other technologies?

S. Michelle Shiller, DO, AP/CP, MGP: In early stage disease, we’re dealing primarily with immunohistochemistry, except for FISH with HER2 status. In the setting in which we’d have an equivocal finding by immunohistochemistry, in keeping with guidelines we would then implement FISH-based testing to further understand and characterize that tumor. The other larger panels start being implemented in more advanced-stage disease, unless we have a triple-negative breast cancer or something like that. When we’re dealing with hormone receptor–positive disease or a definitive HER2 finding, those are the fundamental foundational set of markers that are tested for.

Aditya Bardia, MD, MP: That makes sense because these things are actionable. Is there any role of luminal testing, like PAM50 or molecular subtype? Is that something that’s considered at your institution?

S. Michelle Shiller, DO, AP/CP, MGP: Not regularly. That’s usually driven on the clinical side. It’s a balance. Often it’s driven by the surgical oncologist, but sometimes it’s driven by the oncologist. We’re usually not part of that discussion. A lot of times it’s there to drive clinical decision-making with respect to informing extent of surgical management and/or prognostics with respect to implementing other therapeutic strategies, such as hormones and chemotherapy.

Aditya Bardia, MD, MPH: What about the medical oncology team? Do you do testing for the luminal subtypes or PAM50 besides ER, PR, HER2? Are there other tests at your institution? We’ll start with Virginia.

Virginia Kaklamani, MD: We typically do Oncotype. That’s the test we use to decide whether to offer chemotherapy to our patients. We see some patients from the outside with MammaPrint and some other assays, but this is what we rely on for the early stage setting.

Aditya Bardia, MD, MPH: How about at your institution, Heather? What’s your practice?

Heather McArthur, MD: We do ER, PR, HER2, and Ki-67. In terms of assays, we exclusively use Oncotype, except for very specific instances where we use MammaPrint.

Aditya Bardia, MD, MPH: Are things different on the West Coast, Sara?

Sara A. Hurvitz, MD: No, that’s fairly standard. That’s the approach we utilize. Oncotype is supported by studies like TAILORx and RxPONDER, which are prospective randomized studies that have helped us home in on what therapy we should give a patient based on their score. If they’re postmenopausal, the data are fairly certain. They’re little less certain for the premenopausal group. Though given the amount of validated evidence that we have, that’s our choice.

Transcript edited for clarity.

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