The results from the HER2DX pCR score reveal an inverse relationship between endocrine sensitivity and anti-HER2 sensitivity in HER2-positive/hormone receptor-positive breast cancer; namely, the higher the HER2DX pCR score, the more anti-HER2 sensitive the tumour is, and the less endocrine sensitive it is, and vice-versa. This evidence concerns the gene ERBB2 and neoplasm.