ESR1 and breast cancer: Consistent with this, multivariate survival analysis of ER+ cases using a stepwise Cox regression model including HER2 status, Ki67 status, tumour size and histological grade revealed that SASH1 expression was independently associated with breast cancer specific survival (BCSS) (Table 2; HR = 0.45; 95% confidence interval 0.27–0.77; p = 0.0037).