Abstract P4-09-03: Survival differences between HER2-zero and HER2-low-expressing breast cancer—A meta-analysis of early breast cancer patient data from 12 studies including 39831 patients

Abstract Background: HER2-low-expressing breast cancer takes up 40-50% in all breast cancer subtypes. Survival difference between HER2 low expression and HER2-zero breast cancer remains controversial. Therefore, the aim of this study was to compare the survival outcome of the two subtypes and to explore the impact of hormone receptor status. Methods:A comprehensive medical literature search was performed by PubMed, EMBASE, and the Cochrane Library through June 2022. We included observational studies reporting hazard ratios (HRs) with corresponding 95% confidence intervals (CIs). The results of individual studies were pooled by fixed-effects models. Twelve articles with a total of 39,831 breast cancer patients were included in the meta-analysis. Results:We observed a statistically significant association between low HER2 expression levels and better breast cancer survival outcomes (OS: HR: 0.82; 95% confidence interval: 0.77, 0.88; DFS/RFS: HR: 0.88; 95% confidence interval: 0.83, 0.93). In a subgroup analysis, we found that HER2-low patients had better survival outcomes among hormone receptor-positive breast cancer patients (OS: HR: 0.85; 95% confidence interval: 0.78, 0.92; DFS/RFS: HR: 0.90; 95% confidence interval: 0.84, 0.96). Similarly, in triple-negative breast cancer patients, we also observed a positive association between HER2 low expression and better survival (OS: HR: 0.78; 95% confidence interval: 0.69, 0.87; DFS/RFS: HR: 0.86; 95% confidence interval: 0.77, 0.94). Conclusions: Our study showed that HER2 low expressing breast cancer had better survival outcomes compared to HER2 negative breast cancer in patients with early stage breast cancer, regardless of hormone receptor status. The result has a positive effect on us to further explore the clinical features, molecular characteristics and better treatment strategies of HER2-low-expressing breast cancer. Forest plot of HER2 low expression and overall survival in overall population Forest plot of HER2 low expression and disease free survival or relapse free survival in overall population Citation Format: Xiaoqi Zhang, Ciqiu Yang, Kun Wang. Survival differences between HER2-zero and HER2-low-expressing breast cancer—A meta-analysis of early breast cancer patient data from 12 studies including 39831 patients [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-09-03.