Abstract PO4-17-12: Early adherence to adjuvant abemaciclib: Data from the Belgian Medical Need Program
Authors: Van Houdt Maxime , Michaux Marc , Altintas Sevilay , Awada Ahmad , Canon Jean-Luc , Denys Hannelore , Duhoux François , Jerusalem Guy , Mebis Jeroen , Janssens Rosanne , Huys Isabelle , Liese Barbier , Verbeke Charlotte , Han Sileny , Wildiers Hans , Neven Patrick 
Published: May 2024

Abstract
Patient adherence profiles for adjuvant hormonal therapy combined with abemaciclib in HR+/HER2- High Risk EBC based on real world evidence (RWE) from a Medical Need Program in Belgium
Background
Following results of MonarchE, demonstrating clinically meaningful improvement in invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS), a 2-year treatment with abemaciclib has been reimbursed in Belgium since May 1st, 2023 for the adjuvant treatment of HR+, HER2–, lymph node-positive (&gt;3 or 1-3 if pT3 or grade 3) early breast cancer (EBC). In this trial, adverse event related treatment discontinuation was reported in 18,5% (8.9% after dose reduction) of which 10.1% in the first 5 months after starting this CDK 4/6 inhibitor.
Prior to reimbursement, an early access program was initiated in Belgium on June 28 2022. We studied the proportion of patients estimated to be eligible for the program nationwide who effectively started adjuvant abemaciclib, as well as early treatment discontinuation and dose reductions.
Methods
The number of eligible patients for the adjuvant abemaciclib Medical Need Program (MNP) was estimated by the Belgian Cancer Registry based on the above mentioned reimbursement criteria for patients registered during the incidence year 2018. The MNP was active in Belgium from June 28 2022 until May 1 2023.
Discontinuation rate and proportion with dose reductions were calculated using a nationwide prospective managed monthly updated register of participating patients including information on age at diagnosis, time since therapy start, delivered doses and patient reported adverse events (AE). They all signed an informed consent and agreed to share their registered data after anonymization. Data analysis was retrospective. Descriptive statistics were used.
Results
In this 10-month period, 840 patients were estimated to be eligible to receive adjuvant abemaciclib in Belgium. A total of 311 patients (309 women, 2 men) were included in the program, 37% of the estimated number of patients.
Median age at initiation was 57 y. Median time on treatment was 4.5 months (156 patients &gt;4.5 months on treatment). 21/311 (6.7%) patients discontinued (all causes). 2 patients never started. 10 patients (3.2%) discontinued their therapy without dose reduction. 12/311 (3.8%) had a starting dose of 2 × 100 mg/d. 128/311 (41.1%) had a dose reduction, 96/128 (75%) before 3 months of therapy.
In the subgroup of 156 patients starting treatment &gt;4.5 months ago, 16/156 (10.2%) discontinued treatment, 13 patients have not yet been reported. 79/156 (50.6%) required a dose reduction, of which 7 (4.5%) discontinued after dose reduction.
The reasons for discontinuation reported: 8/21 (38%) gastro-intestinal intolerance, 3/21 (14.2%) real deterioration in renal function, 8/21 quality of life issues (not specified), 1/21 anal burning sensation and anal fistula, 3/21 asthenia and fatigue.
Conclusion
Of the estimated eligible patients in Belgium 37 % started with adjuvant abemaciclib. These results illustrate that there is a need to further improve implementation of adjuvant abemaciclib. Early results show that 89.8% of patients receiving adjuvant abemaciclib therapy in Belgium continued their treatment after 4.5 months and 50% of patients needed a dose reduction. Longer follow-up will be needed. Understanding the reasons of discontinuation and early dose adjustments can enable better patient support on adherence. This is a critical capability to ensure optimal patient compliance.
Citation Format: Maxime Van Houdt, Marc Michaux, Sevilay Altintas, Ahmad Awada, Jean-Luc Canon, Hannelore Denys, François Duhoux, Guy Jerusalem, Jeroen Mebis, Rosanne Janssens, Isabelle Huys, Barbier Liese, Charlotte Verbeke, Sileny Han, Hans Wildiers, Patrick Neven. Early adherence to adjuvant abemaciclib: Data from the Belgian Medical Need Program [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-17-12.