Adding abemaciclib to adjuvant endocrine therapy (ET) can provide long-term benefits for patients with high-risk, hormone receptor (HR)-positive, HER2-negative early breast cancer, according to updated data from the monarchE trial.

Researchers observed improvements in invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS) with abemaciclib that persisted after treatment completion. Overall survival (OS) data were not yet mature.

These findings were presented at the San Antonio Breast Cancer Symposium 2022 by Stephen R.D. Johnston, MBBS, of Royal Marsden NHS Foundation Trust in London, UK.1 The results were simultaneously published in The Lancet Oncology.2


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The data come from a preplanned analysis of monarchE (ClinicalTrials.gov Identifier: NCT03155997). The trial enrolled patients with HR-positive, HER2-negative, node-positive, high-risk early breast cancer. 

Patients were randomly assigned to receive ET for up to 10 years, either alone (n=2829) or in combination with abemaciclib for 2 years (n=2808). At a median follow-up of 42 months, none of the patients were still receiving abemaciclib. 

The updated data showed a sustained benefit in IDFS (hazard ratio [HR], 0.664; 95% CI, 0.578-0.762; P <.0001) and DRFS (HR, 0.659; 95% CI, 0.567-0.767; P <.0001) from abemaciclib beyond the treatment period. 

The 4-year IDFS rate was 85.8% with abemaciclib and 79.4% with ET alone. The 4-year DRFS rate 88.4% and 82.5%, respectively.

The OS data were still immature. However, there were fewer deaths in the abemaciclib arm than in the ET-alone arm (157 and 173, respectively; HR, 0.929; 95% CI, 0.748-1.153; P =.5027). 

“With further follow-up, the Kaplan-Meier curves continue to separate beyond completion of the 2-year treatment period, suggesting a potential carry-over effect [with abemaciclib],”Dr Johnston said. “These data further support the addition of abemaciclib to endocrine therapy for patients with hormone receptor-positive, HER2-negative, node-positive, high-risk, early breast cancer.”

Disclosures: This research was supported by Eli Lilly and Company. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.

References

1. Johnston S, Toi M, O’Shaughnessy J, et al. Abemaciclib plus endocrine therapy for HR+, HER2-, node-positive, high-risk early breast cancer: Results from a pre-planned monarchE overall survival interim analysis, including 4-year efficacy outcomes. Presented at SABCS 2022. December 6-10, 2022. Abstract GS1-09.

2. Johnston S, Toi M, O’Shaughnessy J, et al. Abemaciclib plus endocrine therapy for hormone receptor-positive, HER2-negative, node-positive, high-risk early breast cancer (monarchE): results from a preplanned interim analysis of a randomised, open-label, phase 3 trial. Lancet Oncol. Published online December 7, 2022. doi:https://doi.org/10.1016/S1470-2045(22)00694-5