Key clinical point: Human epidermal growth factor receptor 2 (HER2)-low expression was significantly discordant between early and advanced stages of invasive breast cancer (BC), with the expression being enriched in the advanced stages.
Major finding: Significant discordance in HER2 expression between the primary tumor and matched biopsy samples was observed in the overall population (Cohen’s kappa coefficient (K) 0.33; 95% CI 0.21-0.44) and in subgroups of estrogen receptor-positive (ER+) BC (K 0.32; 95% CI 0.19-0.45) and triple-negative (TN) BC (K 0.18; 95% CI −0.09 to 0.46) with HER2-low expression being enriched in advanced-stage biopsies vs. primary tumors in the overall population (64% vs. 53%), ER+ BC (71% vs. 57%), and TNBC (38% vs. 36%).
Study details: Findings are from a retrospective analysis of 232 patients with HER2-negative invasive BC.
Disclosures: This study was partially funded by the Italian Ministry of Health with Ricerca Corrente. Some of the authors declared serving as an advisor and consultant or receiving honoraria from several sources.
Source: Tarantino P et al. Eur J Cancer. 2022;163:P35-43 (Jan 13). Doi: 10.1016/j.ejca.2021.12.022.