Real-world (RW) elacestrant use patterns and therapeutic outcomes in patients (pts) with hormone receptor-positive (HR+)/HER2-negative advanced breast cancer (aBC).

• DOI: 10.1200/jco.2024.42.16_suppl.1071
• Publication Date: 2024-06-04T17:22:13Z
• Authors: Maxwell Roger Lloyd; Azka Ali; Caroline M. Weipert; Sheila R Solomon; Jayati Saha; Marla Lipsyc-Sharf; Erika P. Hamilton; Kevin Kalinsky; Aditya Bardia; Nicole Zhang; Seth Andrew Wander
• Keywords: HER2 negative

1071 Background: Elacestrant was the first novel endocrine therapy (ET) to receive FDA approval in over two decades. In EMERALD study, pts with ESR1-mutant ( ESR1m) HR+/HER2-negative aBC had a median progression free survival (PFS) of 3.8 months (mos). Here, we use large clinical-genomic database assess RW elacestrant and examine impact line (LOT) number ERS1m on pt outcomes. Methods: Pts HR+/HER2- were identified via GuardantINFORM database; all ESR1m detected circulating tumor DNA (ctDNA) testing done routine clinical care treated after date included. Real-world time treatment discontinuation (TTD) next (TTNT) used as proxies for PFS (measured mos). For TTD/TTNT, Kaplan-Meier curves time-to-event 95% confidence intervals (CI) used. outcomes specific single versus >1 ESR1m, only an within 6 prior start Results: 418 elacestrant, age 62 years. across metastatic LOT (2 nd : 12%, 3 rd 18%, 4 tH 17%, 5 th +: 53%). Considering therapies, commonly received aromatase inhibitors (AI) (89%), CDK4/6i (73%), fulvestrant (63%), chemotherapy (49%). Of 312 start, 56% harbored maximum 11 patient. TTD 5.4 mos (95% CI: 4.2 - not reached [NR]) TTNT 6.2 5.7 NR); most censored at analysis (65% TTD, 71% TTNT). There no significant differences or based mutations (Table 1). Data yet mature ET use, duration exposure, co-occurring alterations. Conclusions: Using database, present early insights elacestrant. Initial outcomes, assessed TTNT, exceed reported trial, perhaps due multiple factors impacting patient selection restaging protocols, which can differ prospective trials care. Factors such did outcomes; additional treatment, will be data matures. [Table: see text]