53P HER2 low by immunohistochemistry (IHC) and gene expression by qRT-PCR using OncotypeDX in ER+ early breast cancer

HER2-low is a novel breast cancer entity, however the ability of proper discrimination between HER2 negative and low still matter debate. This study investigates whether gene expression determined by ODX can differentiate at IHC. Retrospective cohort analysis on 229 patients with early BC tested after surgery in Humanitas Cancer Center Jan 2020 2023. We gathered well-known clinicopathological data, particular IHC, categorized as 0, 1+, 2+ fluorescent situ hybridization (FISH). Difference HER IHC were Wilcoxon test. In our cohort, 53.3% 29.7% 17.0% 2+. Clinical characteristics similar three groups, including age menopausal status without any statistical difference. The median recurrence score (RS) was 21 [IQR: 15-29], 20 (IQR: 15-31), 15.5-28), respectively, for RS > 25 found 42.6% 0 55.6% node-negative no statistically significant difference (p = 0.618). all patients, 9.20 8.70- 9.60]. increased higher broad overlapping groups [HER2 0: 8.90 (IQR 8.5 – 9.28); 1+: 9.40 9.72); 2+: 9.50 9.30 10.0)]. Table 53PHER2 nodal statusHER2 IHCNode negative01+2+pn542918Recurrence Score (%)23 (42.6)14 (48.3)10 (55.6)0.61Recurrence (median [IQR])24.00 [17.25, 31.75]24.00 [17.00, 33.00]27.50 [20.25, 33.50]0.87HER2 [IQR])8.90 [8.50, 9.28]9.20 [8.70, 9.70]9.50 [9.20, 9.78]0.001Node positiven683921Recurrence (%)18 (26.5)8 (20.5)4 (19.0)0.68Recurrence [IQR])17.00 [13.75, 26.25]17.00 [14.00, 24.00]17.00 [13.00, 24.00]0.88HER2 [8.60, 9.22]9.50 [9.15, 9.90]9.60 [9.40, 10.10]<0.001 Open table new tab to be greater but overlap. raises possibility that subgroups varying degrees exist categories which may considered potential target antibody-drug conjugates.