ER-Positive Breast Cancer and ER Testing Strategies

Gary Ulaner, MD, PhD: Hello, my name is Dr Gary Ulaner, and I’m the James and Pamela Muzzy Endowed Chair of Molecular Imaging and Therapy at the Hoag Family Cancer Institute in Irvine, California. It’s my pleasure, on behalf of OncLive®, to welcome you to this webinar, titled “Optimizing Imaging in ER-positive Metastatic Breast Cancer to Improve Clinical Outcomes.” It’s my pleasure to introduce my copresenter, Dr Jeremy Force.

Jeremy Force, DO: Hi, everyone. Thank you for allowing us this opportunity. I’m Dr Jeremy Force. I’m an assistant professor of medicine at Duke University School of Medicine in Durham, North Carolina. I focus on breast cancer and functional precision medicine, and we’re excited to talk to you about the use of functional imaging for ER [estrogen receptor]–positive breast cancer. When looking at the ER+ breast cancer landscape, we know that 70% to 75% of breast cancers diagnosed annually are hormone receptor positive or ER+, mPR [membrane progesterone receptor] positive.

This proportion of patients continues to increase because of therapeutic advancements we’ve made in breast cancer in terms of the prevalence of this disease. Breast cancer is the largest cancer among women in the entire world. This is clearly a problem, and this is clearly an issue for which we need to come up with better therapies and better diagnostics for these women and men with breast cancer, to aid the therapeutic endeavors that they’ll embark on.

The 5-year breast cancer specifics survival rate is still excellent. That also means that more patients may develop metastatic disease as time moves on. In respect to the progress we’ve made from a therapeutic advancement—going back to the 1890s with Sir George Beatson, with oophorectomy, and Dr Elwood Jensen, who discovered the estrogen receptor in the 1950s—there has been a large advancement over the last several decades, moving all the way forward with CDK4/6 pathway. We’ll get into some of the advancement and some of the data around functional imaging, not only the CDK4/6 inhibition pathway but also from an endocrine therapy perspective.

In totality, these drugs have revolutionized the field of ER+ metastatic breast cancer, which is equally great for our patients. When testing for ER+ disease, the hormone receptors that many medical oncologists and other oncologists will refer to are paramount. We’re able to identify the estrogen receptor status of tumors based on biomarkers from immunohistochemistry that we will commonly obtain from biopsies.

Those biopsies may come from primary breast masses or, in this situation, ER+ disease from metastatic sites. These help clarify the hormone receptor status but also delineate and further allow for us to determine which therapies may be appropriate for our patients. These are clearly diagnostic, and they’re predictive of endocrine therapy advantage. In that regard, there are many times that biopsies are challenging to get to. They’re validated, especially immunohistochemistry, and it’s the gold standard of predicting benefit from endocrine therapy. These core biopsies can be challenging, depending upon where they’re at.

Receptions also could be offered to patients, but it depends on which clinical situation and where the disease may lie. PET [positron emission tomography] scans—FDG [fluorodeoxyglucose]–PET scans, specifically—have shown utility in ER+ breast cancers. However, there are subsets for whom there’s a disadvantage using FDG-PET. Also, for indolent disease in general, it might not pick up all the disease that we would see in a metastatic case. Hence, our main discussion will be about the FES-PET, which has…clinical utility, and we’ll move into that moving forward. I’d like to hand this off to my esteemed colleague Dr Ulaner to take us through some of the FES-PET molecular imaging therapies.

Transcript Edited for Clarity