The following article features coverage from the European Society of Medical Oncology (ESMO) 2017 Congress in Madrid, Spain. Click here to read more of Cancer Therapy Advisor’s conference coverage.

Abemaciclib plus letrozole or anastrozole is an effective treatment strategy for patients with HR-positive, HER2-negative advanced breast cancer who have not yet received systemic therapy, according to data presented at the European Society of Medical Oncology (ESMO) 2017 Congress in Spain.1

Abemaciclib is a CDK4/6 inhibitor effective among previously treated patients with advanced breast cancer. For the MONARCH 3 trial ( Identifier: NCT02246621), researchers compared the efficacy of abemaciclib plus anastrozole or letrozole vs placebo plus anastrozole or letrozole among patients not previously treated with a systemic therapy.

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Of 493 enrolled women, 328 were randomly assigned to abemaciclib and 165 were assigned to placebo. All patients had HR-positive, HER2-negative advanced disease; 80.5% of patients had measurable disease and 27.4% received prior neoadjuvant aromatase inhibition.

The median progression-free survival (PFS) was not reached for abemaciclib vs 14.7 months for placebo (hazard ratio, 0.543; P = .000021). The objective response rate (ORR) was 59% in the abemaciclib group vs 44% for placebo.

Adverse events were, however, more common in the abemaciclib group: 81.3% of patients receiving abemaciclib had any-grade diarrhea vs 29.8% in the placebo group; 41.3% of patients receiving abemaciclib had neutropenia vs 1.9% in the placebo group.

The researchers concluded that “abemaciclib + NSAI [a non-steroidal aromatase inhibitor] demonstrated a tolerable safety profile and was an effective initial treatment for [patients] with HR+/HER2- [advanced breast cancer], significantly improving PFS and ORR.”

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Read more of Cancer Therapy Advisor‘s coverage of the European Society of Medical Oncology (ESMO) 2017 Congress by visiting the conference page.


  1. di Leo A, Toi M, Campone M, et al. MONARCH 3: Abemaciclib as initial therapy for patients with HR+/HER2- advanced breast cancer. Presented at: ESMO 2017 Congress; Madrid, Spain: September 8-12, 2017. Abstract 236O_PR.