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

Impact of body mass index (BMI) on efficacy and safety of abemaciclib in patients with breast cancer (BC) treated in the monarchE trial (126562)

Christine Desmedt 1 , Signe Borgquist 2 , Laura Garcia Estévez 3 , Miguel Martin 4 , Stephen Johnston 5 , Fatima Cardoso 6 , Adam M Brufsky 7 , Hakan Harputluoglu 8 , Hung Khong 9 , Belen San Antonio 10 , Jennifer Wei 10 , Maria Munoz Fernandez 10 , Javier Cortés 11 , Fran Boyle 12
  1. Laboratory for Translational Breast Cancer Research, Department of Oncology, KU Leuven, Leuven, Belgium
  2. Department of Oncology, Aarhus University Hospital and Aarhus University, Aarhus, Denmark
  3. Breast Cancer Department, MD Anderson Cancer Center, Madrid, Spain
  4. Hospital General Universitario Gregorio Marañon, Universidad Complutense, Madrid, Spain
  5. Royal Marsden NHS Foundation Trust, London, UK
  6. ABC Global Alliance, Lisbon, Portugal
  7. UPMC Hillman Cancer Center, Pittsburgh, USA
  8. Inonu University, Inonu, Turkey
  9. Banner MD Anderson Cancer Center at Banner Gateway Medical Center, Gilbert, Arizona, USA
  10. Eli Lilly and Company, Indianapolis, Indiana, USA
  11. IOB Institute of Oncology, Quiron Group and Vall d'Hebron Institute of Oncology, Madrid, Spain
  12. Sydney Medical School, University of Sydney, Sydney, NSW, Australia

Two years of adjuvant abemaciclib+endocrine therapy (ET) resulted in sustained improvement in IDFS (HR=0.68,5-year rates:84%vs76% abemaciclib+ET vs ET, 8% absolute benefit) in patients with HR+, HER2-, node-positive, high-risk early BC (EBC) in monarchE. Obesity is an established factor influencing the biology and prognosis of BC. Here we report efficacy/safety by BMI in patients in monarchE.


Patients were randomised 1:1 to receive endocrine therapy (ET) for ≥5 years +/- abemaciclib for 2 years. Groups were defined by baseline BMI (kg/m2): obese (≥30)/overweight (25<30)/non-overweight (<25). IDFS/DRFS in each group was assessed using Kaplan-Meier method and unstratified Cox model.


1507 patients (27%) were obese, 1762 (32%) were overweight, and 2227 (41%) were non-overweight. Most obese patients were postmenopausal (67%), received AI as first ET (75%) and a substantial proportion (47%) had ≥4 comorbidities, vs 60%/69%/34% among overweight patients and 47%/63%/30% among non-overweight, respectively. Patients ≥65 years constituted 18%/17%/12% of these groups. A consistent treatment benefit in IDFS was observed in abemaciclib+ET across all BMI groups: obese (HR=0.67[95%CI:0.53,0.85]), overweight (HR=0.73,95%CI:0.58,0.91), and non-overweight (HR=0.68[95%CI:0.55,0.83]), interaction p-value=0.858. 5-year IDFS rates in the ET arm were lowest in obese patients (74%) and similar for overweight/non-overweight patients (77% in each). With abemaciclib+ET, absolute improvements in IDFS were 8.8%/5.8%/7.9% across each respective BMI group. Similar findings were observed for DRFS. Obese patients had fewer grade≥3 (G≥3) neutropenia (14%vs19%vs24%). Despite higher G≥3 diarrhea in obese patients (10%vs8%vs6%), related dose reductions (18%vs18%vs17%) and discontinuations (5%vs6%vs5%) were similar in all 3 groups. Abemaciclib dose reductions related to AEs were 41%vs43%vs45% in obese/overweight/non-overweight groups, respectively. G≥3 ALT elevations were low in all groups (2%vs3%vs3%). Serious AEs (SAEs) were more common in obese patients, across treatment arms (abemaciclib+ET:20%vs16%vs13%;ET: 11%vs8%vs9%) (fatal SAEs-abemaciclib+ET:3%vs2%vs1%; ET:2%vs1%vs1%).


In patients with high-risk EBC, adjuvant abemaciclib+ET showed consistent and clinically meaningful treatment benefit across BMI subgroups, plus a manageable safety profile.