ERBB2 and breast cancer: However, in the phase III randomised controlled DESTINY-Breast04 trial, T-DXd was shown to have benefits in patients with ‘HER2 low’ breast cancer, defined as a score of 1+ on IHC or as 2+ on IHC with negative ISH, with a hazard ratio of 0.64 for overall survival (95% CI 0.49 to 0.84) [68].