1056 Background: HER2-low expression, defined as HER2 immunohistochemistry (IHC) score of 1+ or 2+ with negative in situ hybridization assay (FISH), accounts for 50% of breast cancers. There is limited and conflicting evidence regarding the efficacy of cyclin-dependent kinase (CDK) 4 and 6 inhibitors in patients with ER+ and HER2-low tumors. This study aimed to investigate the prognostic value of HER2-low expression in patients with ER+/HER2-negative advanced breast cancer treated with CDK 4/6 inhibitors. Methods: We retrospectively selected consecutive patients with ER+/HER2-negative advanced breast cancer treated with CDK 4/6 inhibitors plus endocrine therapy in our institution from May 2015 to Feb 2020. Two cohorts were compared, including HER2-0 (IHC score) and HER2-low (HER2 IHC score 1+ and 2+ [negative FISH]) tumors. Comparisons in progression-free survival (PFS) and overall survival (OS) were performed using a log-rank test. The prognostic value of HER2-low was investigated by the Cox regression model. Results: Among the 186 patients included, median age at treatment was 55 (r 27-84), and majority had ECOG 0 (126, 67.8%). Progesterone receptor was positive in 155 (83.3%) tumors. Of note, most patients received CDK4/6 inhibitors and endocrine therapy as first-line setting (131, 70.4%). Mostly received palbociclib (161, 86.6%), while ribociclib and abemaciclib were used in 23 (12.4%) and 2 (1.08%) patients, respectively. Overall, 27 patients (14.5%) had de novo metastatic disease, 68 (36.6%) had only bone metastases, and 69 (37.1%) had visceral disease. Of the total population, 64 (34.4%) tumors were HER2-low (43 [23.1%] HER2-1+, and 21 [11.3%] HER2-2+), and 122 (65.6%) were HER2-0. Median PFS among patients with HER2-0 and HER-low were 19 mo. (95% CI, 13.9-24.1), and 15.6 mo. (95% CI, 11.1-20.0), p = 0.074, respectively. In patients treated with CDK 4/6 in the first-line setting, no statistically significant differences were observed in terms of PFS and OS between HER2-0 and HER2-low (PFS HR 0.73 [95% CI, 0.47-1.13; p = 0.160], and OS HR 1.04 [95% CI, 0.51-2.14; p = 0.909]). Conclusions: In our study, HER2-low expression did not show a statistically significant impact on patients with ER+/HER2-negative advanced breast cancer treated with CDK 4/6 inhibitors. Our study supports the necessity of real-world evidence and the design of pooled analysis to understand the real implication of this biomarker in patients with ER+/HER2-negative tumors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.