In multivariate analysis, including potentially confounding factors of age, tumour size, stage, grade, NPI, lymphovascular invasion, ER, PR and HER2 status (with individual Kaplan–Meier statistics of P < 0.05 for all variables), caspase-3 expression remained significant for breast cancer-specific survival (hazard ratio (HR) 1.347, 95% confidence interval (CI) 1.086–1.670; P = 0.007) (Table 4). This evidence concerns the gene ERBB2 and breast cancer.