A rapid update to the ASCO guideline on optimal adjuvant chemotherapy and targeted therapy for early breast cancer provides guidance on the use of the oral cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitor abemaciclib with endocrine therapy in patients with high-risk early breast cancer.1 The update incorporates recently published results on the efficacy and safety of abemaciclib in the adjuvant setting that have emerged since the guideline was last updated in 2020.2
“It’s important for clinicians to know about this update because abemaciclib is a new option that can be offered to help improve outcomes among patients with high-risk hormone receptor–positive breast cancer,” said Sharon H. Giordano, MD, MPH, of The University of Texas MD Anderson Cancer Center and Co-Chair of the guideline expert panel.
Sharon H. Giordano, MD, MPH
Abemaciclib received U.S. Food and Drug Administration approval in the adjuvant setting based on findings from the phase III monarchE trial, which demonstrated a significant improvement in invasive disease–free survival with 2 years of abemaciclib plus physicians’ choice of endocrine therapy for at least 5 years vs standard endocrine therapy alone in 5,637 patients with resected, high-risk, hormone receptor–positive, HER2-negative, node-positive breast cancer.2 The improvement in invasive disease–free survival with abemaciclib plus endocrine therapy compared with endocrine therapy alone was observed after a median follow-up of 19 months (hazard ratio [HR] = 0.71) and was maintained after a median follow-up of 27 months (HR = 0.70), yielding a 5.4% absolute improvement in 3-year invasive disease–free survival.3
Subset analyses showed a significant invasive disease–free benefit with the addition of abemaciclib to endocrine therapy among patients with a Ki67 index of at least 20% both in the overall intent-to-treat population and among patients with either at least four positive axillary lymph nodes or with one to three positive axillary lymph nodes and a tumor size ≥ 5 cm or a histologic grade of 3. The most common adverse events associated with abemaciclib plus endocrine therapy were diarrhea, fatigue, and neutropenia.
“It is great to have a new therapy option to consider for those with higher-risk hormone receptor–positive breast cancer. However, as is the case with every therapy decision, the potential harms (or side effects) should be weighed against the anticipated benefits when considering treatment options for each patient,” said Rachel A. Freedman, MD, MPH, of the Dana-Farber Cancer Institute and Co-Chair of the guideline expert panel.
Rachel A. Freedman, MD, MPH
According to the 2021 updated recommendations, 2 years of abemaciclib at 150 mg twice daily plus at least 5 years of endocrine therapy may be offered to patients with hormone receptor–positive, HER2-negative breast cancer, meeting the definitions for higher-risk disease in the monarchE trial.
REFERENCES
1. Giordano SH, Freedman RA, Somerfield MR: Abemaciclib with endocrine therapy in the treatment of high-risk early breast cancer: ASCO optimal adjuvant chemotherapy and targeted therapy guideline rapid recommendation update. J Clin Oncol 40:307-309, 2022.
2. Denduluri N, Somerfield MR, Chavez-MacGregor M, et al: Selection of optimal adjuvant chemotherapy and targeted therapy for early breast cancer: ASCO guideline update. J Clin Oncol 39:685-693, 2020.
3. Harbeck N, Rastogi P, Martin M, et al: Adjuvant abemaciclib combined with endocrine therapy for high-risk early breast cancer: Updated efficacy and Ki67 analysis from the monarchE study. Ann Oncol 32:1571-1581, 2021.
Originally published in ASCO Daily News. © American Society of Clinical Oncology. ASCO Daily News, December 22, 2021. All rights reserved.
