Association of HER2-low expression with efficacy of CDK4/6-inhibitor for HR-positive HER2-negative metastatic breast cancer

A study at Queen Elizabeth Hospital in Hong Kong evaluated impact of the level of HER2 expression on efficacy of CDK4/6 inhibitor for HR-positive, HER2-negative metastatic breast cancer. The study found that low expression of HER2 (IHC 1+ or 2+) was associated with significantly worse PFS compared with no expression of HER2. The authors conclude that HER2-low expression could be a potential marker associated with low efficacy of CDK4/6 inhibition in HR-positive, HER2-negative breast cancer.