Rapports de cas cliniques et médicaux

Response to Checkpoint Blockade in a Patient with Metastatic HER2-positive Breast Cancer

Abstract

Melissa McShane, Lori J. Goldstein and Elias Obeid

The success of immunotherapy in breast cancer care is limited to the triple negative subtype. There are no current recommendations for the use of checkpoint inhibitors in HER2 positive disease; although the tumor biology in HER2-positive breast cancer demonstrates that the immune system has a potentially substantial contribution to the therapeutic effects of trastuzumab. Our group is currently conducting an investigator initiated clinical trial of safety and clinical activity for atezolizumab (a PDL-1 inhibitor) added to standard of care paclitaxel, trastuzumab and pertuzumab for first line treatment of patients with metastatic HER2-positive breast cancer (NCT03125928, PI: LJ Goldstein, co-PI: E Obeid). Our case report demonstrates the successful use of immunotherapy (in this case, pembrolizumab) and trastuzumab in a patient with metastatic HER2-positive breast cancer with low PD-L1 positivity and a high tumor mutational burden seen on Caris testing. This case demonstrates clinical support for the use of this combination and illustrates the importance of continued research to better identify the role of immunotherapy in HER2-positive patients. We believe this report adds significant information to previously published data and alerts treating breast oncologists to such therapies, as the field awaits our and other clinical trials of immunotherapy in metastatic HER2-positive breast cancer.