David Rimm, MD, PHD, senior study author and director of Yale Pathology Tissue Services at the Yale Cancer Center, stated the results suggest a new test needs to be developed to ensure the correct patients are offered trastuzumab deruxtecan.
HER2 breast cancer is diagnosed through a score of one to three. A score of zero or one positive means the breast cancer is HER2 negative; a score of two plus is borderline; and a score of three plus is positive.
Researchers gathered data on assays from 1,400 global laboratories, a College of American Pathologists survey and an assessment of analytic data from a Yale-based study of 170 breast cancer biopsies to determine the effectiveness of trastuzumab deruxtecan as a treatment for breast cancer patients.
The survey results found 19 percent of the cases read by labs generated results with less than 70 percent agreement in a HER2 score of zero versus one positive. There was only 26 percent agreement in the second portion of the study when pathologists observed the biopsies.
