Abstract P1-13-07: De-escalation of five-year adjuvant endocrine therapy in patients with ER-low positive breast cancer: Propensity-matched analysis from a prospectively maintained cohort

Abstract

Abstract Background The standard 5 years of endocrine therapy has shown additional benefits when compared with short-term 2-3 years of treatment in patients with estrogen receptor (ER)-positive breast cancer; however, whether the long-term treatment is still necessary for ER-low positive (1%-10% by immunohistochemistry) breast cancer is unclear. Methods The prospectively maintained Breast Surgery Database of Fudan University Shanghai Cancer Center was used for this propensity-matched analysis. The primary endpoint was disease-free survival (DFS). Multivariate Cox regression and propensity score matching methods were performed to minimize bias. Hazard ratio (HR) with 95% confidence interval (CI) was calculated. All statistics were 2-sided. Results From 2012 to 2017, there were 22768 consecutive women with pathologically confirmed early-stage breast cancer and 1013 (4.45%) were identified as ER-low positive. Among them, 634 cases met the inclusion criteria and were divided into three groups: received no endocrine therapy (n=89); received 2-3 years of endocrine therapy (n=185); and received approximately 5 years of endocrine therapy (n=360). At a median follow-up of 65 months, there was no significant difference in DFS between patients who received 2-3 years and 5 years of endocrine therapy (HR, 0.82; 95% CI: 0.51-1.33; P=0.43). In the multivariate Cox regression analysis of the propensity score-matched samples, the DFS was not significantly better for patients who received 5 years of endocrine therapy than those receiving 2-3 years of treatment (HR, 0.74; 95% CI: 0.41-1.31; P=0.30). Conclusion Short-term 2-3 years of endocrine therapy might be an alternative for ER-low positive breast cancer instead of standard 5 years. Citation Format: Keda Yu, Yuwen Cai, Zhiming Shao. De-escalation of five-year adjuvant endocrine therapy in patients with ER-low positive breast cancer: Propensity-matched analysis from a prospectively maintained cohort [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-13-07.