André, Valérie

This letter to the editor responds to Badoui et al. regarding data on abemaciclib dosages and adverse events.

AbstractThis post hoc analysis of MONARCH 2 and MONARCH 3 assesses the efficacy, safety, and pharmacokinetics (PK) of abemaciclib in combination with endocrine therapy (ET) in East Asian patients with hormone receptor positive (HR+), human epidermal growth factor receptor 2‐negative (HER2−) advanced breast cancer. MONARCH 2 and MONARCH 3 are global, randomized, double‐blind, phase 3 studies of abemaciclib/placebo + fulvestrant and abemaciclib/placebo + nonsteroidal aromatase inhibitor (NSAI, anastrozole or letrozole), respectively. The East Asian population comprised 212 (31.7%) of the 669 intent‐to‐treat (ITT) population in the MONARCH 2 trial and 144 (29.2%) of the 493 ITT patients in the MONARCH 3 trial. In the East Asian population, median progression‐free survival (PFS) was significantly prolonged in the abemaciclib arm compared with placebo in both MONARCH 2 (hazard ratio [HR], 0.520; 95% confidence interval [CI], 0.362 to 0.747; P < .001; median: 21.2 vs 11.6 months) and MONARCH 3 (HR, 0.326; 95% CI, 0.200 to 0.531, P < .001; median: not reached vs 12.82 months). Diarrhea (MONARCH 2: 90%; MONARCH 3: 88%) and neutropenia (MONARCH 2: 68%; MONARCH 3: 58%) were the most frequent adverse events observed in the East Asian populations. Abemaciclib exposures and PK were similar in East Asians and the non‐East Asian populations of both trials. Abemaciclib in combination with ET in the East Asian populations of MONARCH 2 and MONARCH 3 provided consistent results with the ITT populations, demonstrating improvements in efficacy with generally tolerable safety profiles for patients with HR+, HER2− advanced breast cancer.

Abstract Background Abemaciclib demonstrated efficacy in hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer. Here we provide a comprehensive summary of the most common adverse events (AEs), their management, and whether AEs or dose reductions influenced progression-free survival (PFS), in the MONARCH 2 and 3 trials. Materials and Methods Incidence of the most clinically relevant AEs, management, and outcomes were summarized. Time-dependent covariate analyses examined the impact of dose reductions on PFS. PFS was estimated for patients with and without early onset of diarrhea or neutropenia. Results The most frequently reported AE was diarrhea, with clinically significant diarrhea (grade ≥2) reported for 42.8% of patients taking abemaciclib. Median time to onset was 1 week, and duration ranged from 6 to 12 days, depending on grade and study. Diarrhea was adequately managed by antidiarrheal medication (72.8%), dose omissions (17.3%), and reductions (16.7%). The highest rates of grade ≥2 diarrhea were observed in the first cycles and decreased in subsequent cycles. Neutropenia (grade ≥3) occurred in 25.4% of abemaciclib-treated patients. Neutropenia resolved with dose omissions (16.8%) and/or dose reductions (11.2%). Incidence of febrile neutropenia (0.7%) or other relevant grade ≥3 hematological events (&lt;9%) was low. Venous thromboembolic events (5.3%) were primarily treated with anticoagulants. Interstitial lung disease/pneumonitis (3.4%) was treated with corticosteroids and/or antibiotics. PFS benefit of abemaciclib was not impacted by dose reductions or early onset of toxicities. Conclusion Abemaciclib was generally well tolerated. The most common AEs were effectively managed by supportive medications, and/or dose adjustments, with no detriment to PFS. Implications for Practice Treatment with abemaciclib plus fulvestrant or nonsteroidal aromatase inhibitors is generally well tolerated in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer. In MONARCH 2 and MONARCH 3, any-grade diarrhea and grade ≥3 neutropenia were effectively managed with supportive medication and/or dose adjustment. Venous thromboembolic events were treated with anticoagulants and did not often require treatment discontinuation. Interstitial lung disease/pneumonitis was infrequent and treated with corticosteroids and/or antibiotics. Clinicians should be aware of and implement management strategies, including dose adjustments according to local labels, for commonly occurring and serious adverse events to ensure continued treatment and optimize clinical benefit/risk ratio.

Abstract Background MONARCH 3, a phase III trial (NCT02246621) of postmenopausal women with hormone receptor–positive (HR+), human epidermal growth factor receptor 2–negative (HER2−) advanced breast cancer (ABC), previously demonstrated significantly improved progression-free survival in patients receiving abemaciclib plus a nonsteroidal aromatase inhibitor (NSAI). This study evaluated patient-reported outcomes, including global health-related quality of life (HRQoL), functioning, and symptoms. Methods Patients were randomly assigned 2:1 to receive abemaciclib (150 mg twice daily; n = 328) or placebo (n = 165), plus 1 mg anastrozole or 2.5 mg letrozole daily. The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 and Breast Cancer–Specific Quality of Life Questionnaire HRQoL instruments were administered at baseline, every two cycles during cycles 2 through 19 (each cycle being 28 days), every three cycles thereafter, and once at a short-term posttherapy follow-up visit (approximately 30 days after discontinuation). Longitudinal mixed regression and Cox proportional hazards models evaluated postbaseline change and time to sustained deterioration (TTSD), respectively. Results Baseline scores were similar between treatment arms. Although select scores statistically favored the placebo arm, global HRQoL, most symptoms, and functioning scales did not meet the threshold for clinically meaningful differences between treatment arms. Only diarrhea favored the placebo arm with statistically and clinically meaningful differences. There were no TTSD differences between treatment arms for global HRQoL, most symptoms (except diarrhea), or functioning. Conclusion Over a 2-year period, there were no clinically meaningful differences in global HRQoL, functioning, and most symptoms for patients receiving abemaciclib plus NSAI compared with NSAI alone. Only diarrhea favored the placebo arm, consistent with prior safety data, which has been shown to be manageable and reversible. Combined with clinical efficacy, results support treatment with abemaciclib plus NSAI for postmenopausal women with HR+, HER2− ABC. Implications for Practice The addition of abemaciclib to a nonsteroidal aromatase inhibitor (NSAI) was not associated with a clinically meaningful detriment in patient-reported global health-related quality of life, functioning, and most symptoms in postmenopausal women with hormone receptor–positive (HR+), human epidermal growth factor receptor 2–negative (HER2−) advanced breast cancer (ABC). Prior studies have also demonstrated clinical efficacy of abemaciclib plus NSAI compared with NSAI alone, including improved progression-free survival and objective response rate. These results also complement previously reported toxicity data, as measured by investigator-assessed adverse events. Taken together, these results support treatment with abemaciclib plus NSAI for postmenopausal women with HR+, HER2− ABC.