In a multivariate Cox regression analysis after controlling for confounders (such as endocrine therapy, chemotherapy and other validated prognostic factors (ER, PR, HER2, grade, stage, tumour size, TP53 mutation status, PAM50 molecular subtype and IntClust subclasses)), we confirmed that ERCC1 transcript was an independent prognostic factor for OS (p = 0.039) and the interaction between ERCC1 and chemotherapy was also statistically significant (p = 0.020) (Table 2). This evidence concerns the gene ERBB2 and neoplasm.