Abemaciclib Plus Fulvestrant Is Effective Therapy in Endocrine-resistant Breast Cancer

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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.
Patients with breast cancer who progress on endocrine therapy and are then treated with abemaciclib and fulvestrant have a 45% decreased risk for progression.
The following article features coverage from the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, Illinois. Click here to read more of Cancer Therapy Advisor's conference coverage.

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.

RELATED: Buparlisib Plus Fulvestrant Effective But Increases Toxicity in Breast Cancer

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.

Reference

  1. 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).

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