The survival analyses were stratified for ER-status, and for patients with an ER negative DCIS, HER2 positivity predicted a significantly lower risk of IBCR (Log-Rank, P = 0.003), (Fig. 3a), which was not the case for ER positive DCIS patients (Log-Rank, P = 0.76), (Fig. 3b). This evidence concerns the gene ESR1 and ductal breast carcinoma in situ.