Key clinical point: In estrogen receptor-positive/human epidermal growth factor receptor-positive (ER+/HER2+) breast cancer (BC), HER2-enriched (HER2-E) tumors were more likely to respond poorly to aromatase inhibitor (AI) therapy and pose an increased risk for disease recurrence.
Major finding: AI-treated HER2-E tumors were associated with poorer Ki67 response and higher Ki67 expression level at 2-weeks timepoint compared with luminal A and B tumors (odds ratio 1.52-12.31; false discovery rate < 0.0001). HER2-E subtype was an independent predictor of shorter time to recurrence (hazard ratio 2.55; P = .022).
Study details: Findings are from the phase 3 POETIC trial including 342 patients with early ER+/HER2+ BC who were assigned to 2 weeks of perisurgical AI (n = 237) or no AI (n = 105).
Disclosures: This study was funded by Cancer Research UK. Some authors declared holding or filing patents or receiving grants, nonfinancial support, consulting fees, honoraria, or research funding from several sources.
Source: Bergamino MA et al. HER2-enriched subtype and novel molecular subgroups drive aromatase inhibitor resistance and an increased risk of relapse in early ER+/HER2+ breast cancer. EBioMedicine. 2022;83:104205 (Aug 16). Doi: 10.1016/j.ebiom.2022.104205