Abstract PS18-22: Association of molecular biomarkers heterogeneity and treatment pattern, disease outcomes in multifocal or multicentric breast cancer patients

Abstract

Abstract Background: To evaluate the rates of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and Ki-67 heterogeneity in multifocal or multicentric breast cancer (MMBC) and its association with treatment pattern and disease outcomes.Methods: MMBC patients with ER, PR, HER2, and Ki67 results for each tumor focus were retrospectively analyzed. Patients with concordant ER, PR, HER2, and Ki67 status among all invasive tumor foci were categorized into the Homo group, while the rest were defined as the Hetero group. Chi-square or Fisher test were performed to compare the treatment options between the Hetero and Homo groups. Disease-free survival (DFS) and overall survival (OS) rates were estimated from Kaplan-Meier curves and compared between two groups.Results: A total of 330 patients were included. Concordance rates of ER, PR, HER2, Ki67, and molecular subtype were 97.0%, 93.9%, 96.5%, 91.2%, and 88.2%, respectively (all P values < 0.001). There were 53 (16.1%) and 287 (83.9%) patients classified into the Hetero and Homo groups. Adjuvant endocrine therapy was more frequently assigned for patients in the Hetero group than in the Homo group (84.9% vs. 71.7%, P = 0.046). There was no difference in terms of adjuvant anti-HER2 therapy (28.3% vs. 19.6%, P = 0.196) and chemotherapy (69.9% vs. 69.8%, P = 0.987) usage between two groups. At a median follow-up of 36 months, DFS rates were 81.2% for the Hetero group and 96.5% for the Homo group (HR = 2.81, 95% CI: 1.00-7.88, P = 0.041). The estimated 3-year OS rates for these two groups were 95.8% and 99.5%, respectively (HR = 4.31, 95% CI: 0.83-22.46, P = 0.059).Conclusion: Heterogeneity of ER, PR, HER2, or Ki67 was present in 16.1% patients with MMBC. Biomarkers heterogeneity influenced adjuvant endocrine therapy usage and was associated with worse disease outcomes, indicating further clinical evaluation. Citation Format: Shuai Li, Jiayi Wu, Ou Huang, Jianrong He, Li Zhu, Weiguo Chen, Yafen Li, Xiaosong Chen, Kunwei Shen. Association of molecular biomarkers heterogeneity and treatment pattern, disease outcomes in multifocal or multicentric breast cancer patients [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS18-22.