Efficacy of Oral SERDs in the treatment of ER+, HER2 - metastatic breast cancer, a stratified analysis of the ESR1 wild type and mutant subgroups

N Z H Wong; D W T Yap; R J M Ong; J J Zhao; Y H Chan; J C S Tey; R Sundar; J S J Lim; S S Dawood

doi:10.1016/j.annonc.2023.10.122

Efficacy of Oral SERDs in the treatment of ER+, HER2 - metastatic breast cancer, a stratified analysis of the ESR1 wild type and mutant subgroups

Ann Oncol. 2023 Oct 21:S0923-7534(23)04328-4. doi: 10.1016/j.annonc.2023.10.122. Online ahead of print.

Authors

N Z H Wong¹, D W T Yap¹, R J M Ong¹, J J Zhao², Y H Chan³, J C S Tey⁴, R Sundar⁵, J S J Lim⁶, S S Dawood⁷

Affiliations

¹ Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
² Department of Haematology-Oncology, National University Cancer Institute, National University Hospital, Singapore.
³ Biostatistics Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
⁴ Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Department of Radiation Oncology, National University Cancer Institute, National University Hospital, Singapore.
⁵ Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Department of Haematology-Oncology, National University Cancer Institute, National University Hospital, Singapore; Cancer and Stem Cell Biology Program, Duke-NUS Medical School, Singapore; The N.1 Institute for Health, National University of Singapore, Singapore.
⁶ Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Department of Haematology-Oncology, National University Cancer Institute, National University Hospital, Singapore; Cancer Science Institute, National University of Singapore, Singapore, Singapore. Electronic address: csilsjj@nus.edu.sg.
⁷ Mediclinic City Hospital Dubai. Electronic address: shaheenah_d@yahoo.com.

PMID: 37871699
DOI: 10.1016/j.annonc.2023.10.122

Abstract

Background: Oral SERDs are a novel drug class that have been developed to counteract resistance due to ESR1 mutations. Several SERDs have emerged from phase 2 and 3 trials, with the FDA limiting approval for Elacestrant to patients with ESR1mt tumours despite PFS benefit in the overall population. However, questions remain on whether patients with ESR1wt tumours stand to benefit from oral SERDs.

Patients and methods: Manuscripts and conference presentations of Randomised Controlled Trials were extracted after a systematic search of Embase, PubMed and Cochrane from inception until January 21,2023. RCTs investigating the efficacy of oral SERDs versus endocrine therapy for ER positive, HER2 negative advanced breast cancer, and which reported the Kaplan Meier (KM) curves of PFS in the overall and ESR1 mutant (ESR1mt) population were selected. A graphical reconstructive algorithm was applied to estimate time-to-event outcomes from reported KM curves in all overall and ESR1mt cohorts. A bipartite matching algorithm, KMSubtraction, was used to derive survival data for unreported (ESR1wt) subgroups. An individual patient data (IPD) meta-analysis was then pursued, pooling data by ESR1 mutation status in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Cochrane Guidelines for IPD.

Results: The randomized clinical trials ACELERA, AMEERA-3, EMERALD and SERENA-2 were included, totalling 1290 patients. In the pooled analysis of the overall cohort, PFS benefit was observed with oral SERDs when compared with treatment of physicians choice (TPC) (HR 0.783, 95%CI 0.681-0.900, p<0.001). In the ESR1mt subgroup, oral SERDs demonstrated improved PFS (HR 0.557, 95%CI 0.440-0.705, p<0.001) compared to TPC. In the ESR1wt subgroup, oral SERDs demonstrated no significant PFS benefit (HR 0.944, 95%CI 0.783-1.138, p=0.543) when compared to TPC.

Conclusions: The results of this IPD meta-analysis suggests that PFS benefit in the overall population is mainly driven by the ESR1mt subgroup.

Keywords: ER positive; ESR1; Metastatic Breast Cancer; SERD.