Abemaciclib Plus Fulvestrant Is Effective Therapy in Endocrine-resistant Breast Cancer
Patients with breast cancer who progress on endocrine therapy and are then treated with abemaciclib and fulvestrant have a 45% decreased risk for progression.
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Patients with breast cancer who progress on endocrine therapy and are then treated with abemaciclib and fulvestrant have a 45% decreased risk for progression, according data from the MONARCH 2 trial (ClinicalTrials.gov Identifier: NCT02107703) presented at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago.1
Data for MONARCH 2 were presented by George W. Sledge, MD, of Stanford University in California. Abemaciclib is an investigational third-generation CKD4 and CDK6 inhibitor that is being evaluated across a wide range of cancers.
In the phase 3 MONARCH 2 trial, women with HR+/HER2- breast cancer were randomly assigned in a 2:1 ratio to receive abemaciclib + fulvestrant (446 patients) or placebo with fulvestrant (223 patients).
Abemaciclib was initially given at a dose of 200 mg twice daily. But the incidence of diarrhea seen in the first 121 patients provided for protocol amendment. All subsequent patients received abemaciclib 150 mg twice daily; fulvestrant 500 mg was provided as per label.
At baseline, median age was about 60 years; 25% of patients showed primary resistance to endocrine therapy, 82% were postmenopausal, 56% had visceral disease, and 72% had measureable disease.
Median progression-free survival was 16.4 months for patients on abemaciclib with fulvestrant and 9.3 months for those on placebo with fulvestrant (P < .0000001). Median duration of response was not reached for patients on abemaciclib with fulvestrant and was 25.6 months for those on placebo with fulvestrant.
In the intention-to-treat population, objective response rate (ORR) was 35.2% for the abemaciclib combination vs 16.1% for patients on fulvestrant alone. Among patients with measurable disease, ORR was 48.1% with the combination and 21.3% with fulvestrant alone.
Patients on abemaciclib with fulvestrant (vs placebo with fulvestrant) had a higher incidence of diarrhea (86.4% vs 24.7%), neutropenia (46.0% vs 4.0%), nausea (45.1% vs 22.9%), and fatigue (39.9% vs 26.9%). Grade 3/4 diarrhea and neutropenia (vs fulvestrant only) were 13.4% (0.4%) and 26.5% (1.7%), respectively.
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Treatment discontinuation was reported in 15.9% of patients receiving the abiraterone combination (vs 3.1% for fulvestrant).
Read more of Cancer Therapy Advisor's coverage of the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting by visiting the conference page.
- Sledge GW, Toi M, Neven P, et al. MONARCH 2: Abemaciclib in combination with fulvestrant in patients with HR+/HER2- advanced breast cancer who progressed on endocrine therapy. J Clin Oncol. 2017;34(suppl; abstr 1000).