An increase of ERα (OR = 2.15, 95% CI: 1.2–5.91), HER2 (OR = 72.48, 95% CI: 2.36–14,948,598) and E-Cadherin-pSer838/840 (OR = 1.84, 95% CI: 1.15 to 3.55) by one level more than doubled the odds of BC-PDMs responding to PAB therapy (Figure S4H; Table S10; p < 0.01 [Wald, LRT]). Here, ESR1 is linked to breast cancer.