ESR1 and obesity due to melanocortin 4 receptor deficiency: In ER/HER2-stratified analyses, we observed lower pCR odds among women with obesity and HER2+ tumors (ORadj=0.72 [95%CI = 0.47–1.12]) compared with their normal weight counterparts, but no notable association appeared for ER+/HER2- (ORadj=0.97 [95%CI = 0.49–1.96]) and ER-/HER2- tumors (ORadj=0.88 [95%CI = 0.49–1.57]).