Poster Presentation 2025 Joint Meeting of the COSA ASM and IPOS Congress

Patient-reported outcomes (PROs) in patients with ER+, HER2- advanced breast cancer (ABC) treated with imlunestrant, investigator’s choice standard endocrine therapy, or imlunestrant+abemaciclib: Results from the phase III EMBER-3 trial (#417)

Joyce O'Shaughnessy 1 , François-Clément Bidard 2 , Sung-Bae Kim 3 , Eriko Tokunaga 4 , Philippe Aftimos 5 , Cristina Saura 6 , Lisa A Carey 7 , Meena Okera 8 , Everton Melo 9 , Flora Zagouri 10 , Manuel Ernesto Magallanes Maciel 11 , Nuri Karadurmus 12 , Shakeela Bahadur 13 , Rebecca M Soeck 14 , Xuejing Aimee Wang 14 , Suzanne Young 14 , Komal L Jhaveri 15 16 , Nadia Harbeck 17 18 , Dion Marinkovich 19
  1. Baylor University Medical Center, Texas Oncology, US Oncology, Dallas, Texas, USA
  2. Institut Curie and University of Versailles Saint-Quentin-en-Yvelines-Paris-Saclay University, Paris, France
  3. Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of South Korea
  4. National Hospital Organization (NHO) Kyushu Cancer Center, Fukuoka, Japan
  5. Institut Jules Bordet Hôpital Universitaire de Bruxelles, Brussels, Belgium
  6. Vall d'Hebron University Hospital, Vall d'Hebron Institute of Oncology, Barcelona, Spain
  7. University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
  8. Cancer Research SA, Adelaide, South Australia, Australia
  9. Hospital do Câncer de Londrina, Londrina, Brazil
  10. Department of Clinical Therapeutics, Medical School of National and Kapodistrian University of Athens, “Alexandra” General Hospital of Athens, Athens, Greece
  11. Centro Oncologico Internacional, Mexico City, Mexico
  12. Gülhane Education and Research Hospital, University of Health Sciences, Ankara, Turkey
  13. Mayo Clinic Arizona, Scottsdale, Arizona, USA
  14. Eli Lilly and Company, Indianapolis, Indiana, USA
  15. Memorial Sloan Kettering Cancer Center , New York, USA
  16. Weill Cornell Medical College , New York, USA
  17. Brustzentrum, Frauenklinik and CCC Munich, LMU University Hospital, Munich, Germany
  18. Ludwig Maximilians University Munich University Hospital, Munich, Germany
  19. Eli Lilly and Company Australia, Australia

In EMBER-3, patients with ER+, HER2- ABC with disease progression on or after aromatase inhibitor-based therapy, achieved significant PFS improvement with imlunestrant vs standard therapy (SOC: fulvestrant/exemestane) in patients with ESR1 mutations (ESR1m), and with imlunestrant+abemaciclib vs imlunestrant in all patients, regardless of ESR1m. Exploratory PRO analyses are presented here.

EORTC QLQ-C30 was administered at baseline and every 8 weeks until treatment discontinuation, with a longitudinal mixed model for repeated measures used to calculate mean change difference (MCD) from baseline. A 10-point change or difference was defined as clinically meaningful. PRO-CTCAE (diarrhea frequency) was administered weekly (0 [never] - 4 [almost constantly]). PRO-CTCAE (injection site reaction [ISR]) was administered to fulvestrant recipients weekly for 2 weeks post-injection (yes/no [pain/swelling/redness]).

In patients with ESR1m, EORTC QLQ-C30 scores were generally maintained, with treatment differences favoring imlunestrant vs SOC. Patients with ESR1m on imlunestrant had improved global health status (GHS)/QOL and physical function (PF) scores from baseline, while scores with SOC declined (MCD between treatments:7.4 [1.3,13.6]; 4.0 [-0.7,8.7]). In the overall population, GHS/QOL and functional scores were generally maintained, with treatment differences favoring imlunestrant vs SOC vs imlunestrant+abemaciclib. Most fulvestrant recipients (72%) reported ISR at any time while on treatment, with 47% reporting ISR at the majority of their assessments. Patients reported similarly low rates of “frequent” or “almost constant” diarrhea with imlunestrant (3%) and SOC (2%) and higher rates with imlunestrant+abemaciclib (22%).

GHS/QOL and PF were maintained across treatment arms in the EMBER-3 trial, despite the increased frequency of diarrhea in the imlunestrant+abemaciclib arm. The importance of ISR as a clinically relevant AE is demonstrated by the high incidence of patient-reported ISR with fulvestrant. These results support the efficacy and safety of imlunestrant as monotherapy or combined with abemaciclib as an all-oral targeted therapy option.