Abstract 5247: Using real-world data to evaluate the performance of endocrine therapies in ER+/Her2- metastatic breast cancer patients
Authors: Chen Tenghui , Zhang Zhaojie , Gao Lei , Scholz Catherine , Gualberto Antonio , Yu Lihua , Yu Kun 
Published: June 2022

Abstract
Background Real-world data (RWD) has been increasingly used in drug development. A reliable evaluation of efficacy for current treatments is challenging with very limited publication data of clinical trials available. The RWD provides a unique value and an alternative way to achieve such goal. Use data from metastatic Breast Cancer (mBC) patients in the real world clinical practice, we examine the treatment patterns and durations of different endocrine monotherapies in various clinical settings.
Methods We obtained Flatiron Health subject-level mBC data set which consists a group of 20645 mBC patients. The analysis set consisted of subjects who were ER+/Her2-/(PgR+ or PgR-), received at least one prior line of CDK4/6 inhibitor (mono or combo) and one prior line of endocrine therapy (mono or combo) in the mBC settings, and had an ECOG performance score&lt;=2. Time to treatment discontinuation (TTD) was used as real world endpoint. We assessed the median TTD of endocrine monotherapies in various mBC ER+/Her2- patient subgroups using Kaplan-Meier estimates.
Result Out of all subjects in the mBC RWD database, 263 subjects met the inclusion criteria and were included in the analysis set. Among all 263 ER+/Her2- subjects, the median TTD of endocrine monotherapies was 3.0 months (95% CI: 2.8-3.7 months, N=263) in all subjects, 3.7 months (95% CI: 3.0-4.3 months, N=186) in PgR+ group and 2.1 months (95% CI: 1.9-2.9 months, N=77) in PgR- group. Among 186 ER+/PgR+/Her2- subjects, 1) the median TTD of endocrine monotherapies was 3.3 months (95% CI: 2.8-4.6 months, N=153) in ECOG&lt;=1 group and 3.7 months (95% CI: 3.2-6.0 months, N=33) in ECOG=2 group; 2) the median TTD of endocrine monotherapies was 3.4 months (95% CI: 2.3-5.4 months, N=47) in Aromatase inhibitors group, 3.7 months (95% CI: 2.8-5.6 months, N=110) in Fulvestrant group, and 3.1 months (95% CI: 2.3-6.0 months, N=29) in Tamoxifen group; 3) the median TTD of endocrine monotherapies was 3.6 months (95% CI: 2.8-5.9 months, N=74) in one prior treatment line group, 3.7 months (95% CI: 2.0-6.0 months, N=57) in two prior treatment lines group, and 3.7 months (95% CI: 2.3-5.4 months, N=55) in &gt;=3 prior treatment lines group.
Conclusion By investigating the RWD, we observed that the PgR status is prognostic in post CDK setting: endocrine monotherapies in PgR+ group has longer TTD compared to PgR- group in ER+/Her2- mBC subjects. By further looking into ER+/PgR+/Her2- subjects, we observed different treatment durations of endocrine therapies in various clinical scenarios, which may provide a helpful understanding of the mBC monotherapy treatments.
Citation Format: Tenghui Chen, Zhaojie Zhang, Lei Gao, Catherine Scholz, Antonio Gualberto, Lihua Yu, Kun Yu. Using real-world data to evaluate the performance of endocrine therapies in ER+/Her2- metastatic breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5247.