The analysis revealed a strong correlation (Pearson correlation coefficient = 0.89, p < 0.001) between both gene lists, suggesting that anti-HER2 therapies have a higher impact on molecular tumor changes at day 14 than endocrine therapy (Supplementary Fig. 1d), although we cannot exclude an additive or a synergistic effect between anti-HER2 therapy and endocrine therapy in this group of patients. Here, ERBB2 is linked to neoplasm.