ESR1 and breast cancer: Likewise, the multivariable analysis including high or low TIL levels (cut-off value of 30%) as a confounding factor (multivariable model 2 in Table 3) showed that HER2 IHC 3+ (OR, 4.93; 95% CI, 2.06–11.82; p < 0.001), high TIL levels (OR, 3.24; 95% CI, 1.37–7.66; p = 0.007), and low ER expression (1–9%, OR, 4.96; 95% CI, 1.36–18.07; p = 0.015) were independent predictive factors for pCR in ER-positive breast cancer.