Abstract PO3-11-12: A Pragmatic Randomized Trial Comparing Morning versus Evening Dosing of Endocrine Therapy for Early Breast Cancer: Final Results (REaCT-CHRONO Study)

Abstract Background. Interventions to improve tolerability and adherence to endocrine therapy (ET) are critical to the global improvement of breast cancer (BC) survivorship. The optimal time of day to take ET in terms of quality of life, side effects and adherence is unknown. This study compared a morning dose versus an evening dose of ET in patients with early-stage BC (EBC). Methods. In this pragmatic, open-label, multicenter trial, patients with hormone receptor-positive (HR+) EBC were randomized (1:1) to receive either a morning dose (within 1 hour of the patient wake up time) or an evening dose of ET (within 1 hour of patient bedtime). The primary endpoint was endocrine toxicity/tolerability measured by the change in total Functional Assessment of Cancer Therapy-Endocrine Subscale (FACT-ES) score from baseline (commencement of ET) to 12 weeks. The secondary endpoints included: ET toxicity/tolerability and quality of life (FACT-ES and FACT-B) from baseline to 4, 8, 12 and 52 weeks, non-persistence or non-adherence, and patient timing preference. Results. Between June 2021 and March 2022, 245 eligible patients were randomized, 122 to morning (122/245, 49.8%) and 123 to evening (123/245, 50.2%) dosing. Mean age was 61 [standard deviation (sd) 11.9], 181 patients (73.9%) were postmenopausal, 188 (76.7%) received tamoxifen, 58 (23.7%) received an aromatase inhibitor and 22 (9%) received luteinizing hormone-releasing hormone. The mean changes in the FACT-ES score from baseline to 12 weeks following the beginning of ET were -2.0 (sd=14.3) vs -5.4 (sd=16.8) in the morning vs evening arms respectively (Wilcoxon two-sample rank sum test p-value=0.22). Also, the proportion of patients with a clinically important increase (Fisher’s exact test p-value=0.54 0.89) or decrease (p-value= 0.89) in FACT-ES Scores was not statistically different between the arms. At 52 weeks, the mean changes in the FACT-ES score from baseline were -2.5 (sd=18.8) vs -4.8 (sd=15.5) in the morning vs evening arms respectively (p-value=0.23). There was no statistical difference in FACT-ES and FACT-B scores over the 52 weeks of the study. At 12 weeks, 94.5% (69/79) vs 98.7% (78/79) were still taking the ET (p-value=0.2), whereas at 52 weeks, 92.1% (58/63) vs 85.4% (41/48) were still taking ET (p-value=0.36), in the morning vs evening arms respectively. Also, 13.7% (10/73) vs 7.6% (6/79) and 3.2% (2/62) vs 12.5% (6/48) interrupted their ET at least once, in the morning vs evening arms, at 12 and 52 weeks respectively. At week 52, 57.9% (62/107) in the morning arm vs 13.5% (14/104) in the evening arm strongly preferred an ET morning dose, whereas 7.5% (8/107) vs 42.3% (44/104) strongly preferred an ET evening dose. No significant preference changes were observed in dose timing from baseline to week 52 (p-value=0.081). Conclusions. These results suggest no significant difference in quality of life or adherence if ET is taken in the morning or in the evening. Patients should be reassured that they can take ET at their preferred time. Clinical Trial Registration: NCT04864405 Table 1. Mean changes between FACT scores at 12 weeks and 52 weeks from baseline for patients receiving ET morning vs evening dose. A positive value indicates the FACT score increased over time. FACT ES: Endocrine Subscale; FACT B: breast Citation Format: Marie-France Savard, Mohammed Ibrahim, Gregory Pond, Deanna Saunders, Lisa Vandermeer, Lesley Fallowfield, Terry Ng, Arif Awan, Sandeep Sehdev, Ana-Alicia Beltran-Bless, Mark Clemons. A Pragmatic Randomized Trial Comparing Morning versus Evening Dosing of Endocrine Therapy for Early Breast Cancer: Final Results (REaCT-CHRONO Study) [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 PO3-11-12.