Trastuzumab deruxtecan (T-DXd) has shown efficacy in patients with breast cancer with ERBB2 immunohistochemistry (IHC) scores of 1+ or 2+ but not 0 as read in central pathology laboratories. The drug is currently being tested in large randomized clinical trials with registration intent for this patient population. To determine the suitability of the current standard ERBB2 IHC assays to select patients with low ERBB2 positivity for treatment with T-DXd. Assessment of data from College of American Pathologists surveys and assessment of analytic data from a Yale University-based study of concordance of 18 pathologists reading 170 breast cancer biopsies. The total survey data set included scores over 2 years from 1391 to 1452 laboratories of 40 ERBB2 cores from each laboratory (20 cores twice a year for a total of 80). College of American Pathologists surveys show that 19% of cases read by the laboratories generate results with less than or equal to 70% concordance for IHC ERBB2 score 0 vs 1+. When 18 pathologists read the scanned slides from a selected set of breast cancer biopsies using a 4-point scale, there was only 26% concordance between 0 and 1+ compared with 58% concordance between 2+ and 3+. In this study using a current standard ERBB2 IHC assay, the scoring accuracy for ERBB2 IHC in the low range (0 and 1+) was poor. This inaccuracy in the real world could lead to misassignment of many patients for treatment with T-DXd.

Examination of Low ERBB2 Protein Expression in Breast Cancer Tissue

Department of Pathology, Yale University School of Medicine, New Haven, Connecticut

Department of Pathology, The University of Iowa, Iowa City

Department of Pathology, Brigham and Women’s Hospital, Boston, Massachusetts

Department of Pathology, University of California, San Diego

Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia

Department of Pathology, Medical College of Wisconsin, Milwaukee

Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York

Department of Pathology, Massachusetts General Hospital, Boston

Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee

Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis

Department of Pathology, Norton Healthcare, Louisville, Kentucky

Department of Pathology and Laboratory Medicine, Brown University, Providence, Rhode Island

Department of Pathology, Oregon Health & Science University, Portland

Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania

Department of Pathology, University of Alabama at Birmingham

Department of Pathology, MD Anderson Cancer Center, Houston, Texas

Department of Internal Medicine (Medical Oncology), Yale University School of Medicine, New Haven, Connecticut

Examination of Low ERBB2 Protein Expression in Breast Cancer Tissue

Scan to connect with one of our mobile apps

Coinbase Wallet app

Coinbase app

Or try the Coinbase Wallet browser extension