Navigating HER2+ Metastatic Breast Cancer Treatment

Sara M. Tolaney, MD, MPH, introduces the role of HER2 as a breast cancer cell growth receptor and explains HER2-positive versus HER2-negative.

Sara M. Tolaney, MD, MPH, states that all breast cancers should be tested for estrogen, progesterone, and HER2 receptors; HER2 testing involves an immunohistochemistry stain to quantify protein levels, with 3+ indicating HER2+ disease, 0 indicating HER2- disease, and 1-2+ levels needing additional FISH testing to clarify HER2 status.

Sara M. Tolaney, MD, MPH explains that treatment decisions for metastatic breast cancer are based on the current biopsy showing receptor status, but prior biopsies over the full course of disease are considered as well, particularly for HER2 targeted therapies which may work even if HER2 low expression occurred years earlier.

Clinical trials should be considered at any point in a patient's journey with HER2-positive metastatic breast cancer, not just when standard options are exhausted, as they provide early access to promising therapies, novel combinations, and cutting-edge care.

Dr Sara M. Tolaney reviews the currently available treatment options for HER2-positive metastatic breast cancer and notes that many new HER2-targeting antibody-drug conjugates and bispecific antibodies are in development.

Treatment for HER2-negative metastatic breast cancer depends on factors like hormone receptor status, with chemo/immunotherapy for PD-L1-positive triple negative disease, PARP inhibitors for BRCA mutations, and antibody-drug conjugates as options after first line therapy.

Treatment for HER2 low metastatic breast cancer may utilize HER2-targeted antibody-drug conjugates like T-DM1 and sacituzumab govitecan after initial therapy; knowing HER2 status, even low expression, is critical to guide use of these HER2-directed ADCs after chemotherapy.

HER2-targeted therapies improve outcomes by shutting down growth signaling to cancer cells, targeted delivery of chemotherapy, or blocking intracellular signaling - all leveraging the HER2 receptor to better control metastatic breast cancer.

Imaging scans provide an invaluable method of monitoring response to HER2-positive breast cancer treatment; frequency of imaging scans depends on individual patient response, symptoms, and the need to monitor for side effects such as interstitial lung disease.

Patients on HER2-targeted therapies for HER2-positive metastatic breast cancer should be vigilant about potential side effects like heart toxicities and interstitial lung disease and should undergo regular heart function monitoring and lung scans to catch these side effects early.

Patients with metastatic breast cancer receiving HER2-targeted therapies should promptly report any respiratory symptoms or signs of lung and heart disease to their oncology care team to facilitate early intervention and management of side effects.