Abstract P3-05-51: Patients with low expression of BCL 2 experience more late recurrence than patients who do not, which neutralized the protective effect of low BCL2 expression in patients with estrogen receptor positive breast cancer

Abstract Background) BCL2 is a key factor for the regulation of cellular apoptosis and its overexpression inhibits apoptotic cell death and activates cellular proliferation, resulting tumor progression. Although BCL2 are expected to be associated with an adverse prognosis in breast cancer, previous studies have reported inconsistent results and some reported even favorable features. The aim of this study is to investigate what characteristics of BCL2 yield this discrepant result in patients with breast cancer. Materials and methods) Female patients with breast cancer who completed primary treatment against breast cancer between 2003 and 2018 at Wonju Severance Hospital, Korea, were included. Clinocopathological characteristics including BCL2 expression were collected. Patients were categorized into two groups, BCL2 expression in more or less than 10% of tumor cells. Kaplan-Meier curves were generated to compare recurrence-free interval (RFI) and overall survival (OS). Result) The final cohort included 616 patients with a mean age of 54.79±11.2 (25-86) years. Patients with estrogen receptor positive breast cancer were more frequent in patients with tumor in which BCL2 was expressed in less than 10% of tumor cells (70.7% vs. 57.7%). Patients with tumor in which BCL2 was expressed in less than 10% of tumor cells showed better survival than their counterpart. Subgroup analysis according to the estrogen receptor and HER2 overexpression status was done. In patients with tumor in which HER2 was not overexpressed, patients with tumors in which BCL2 expressed less than 10% of tumor cells showed better survival(p=0.007). Survival difference maintained in patients with triple negative disease(p=0.010). However, in patients with estrogen receptor positive breast cancer, survival of two groups of patients with high and low BCL2 expression become not significant over time as late recurrence occurred (p=0.227). In contrast, patients with HER2 positive disease breast cancer showed worse prognosis than their counterpart when their tumor showed BCL2 expression in less than 10% of tumor cells. Conclusion) BCL2 overexpression showed different contribution to the patients’ survival according to the subtypes. Patients with HER2 overexpression showed better survival when BCL2 was overexpressed and patients with HER2 negative disease does not. First, similar survival was resulted from late recurrence in patients with estrogen receptor positive disease. Second, apoptotic capacity of tumor cells may not be major survival factor if tumor cells are exactly targeted. Citation Format: Hyang Suk Choi, Hany Hany Noh, In-Jeong Cho In-Jeong Cho, Seung Taek Lim, Jong-In Lee, Airi Han. Patients with low expression of BCL 2 experience more late recurrence than patients who do not, which neutralized the protective effect of low BCL2 expression in patients with estrogen receptor positive breast cancer [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 P3-05-51.