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William J. Gradishar, MD, FACP, FASCO


CDK Inhibition Plus Endocrine Therapy for Breast Cancer: Case Presentations

By: Julia Fiederlein
Posted: Friday, June 3, 2022

David Hicks, MD, and Ruth M. O’Regan, MD, both of the University of Rochester, New York, sought to determine whether adding a CDK4/6 inhibitor to endocrine therapy may benefit patients with high-risk, node-positive, hormone receptor–positive breast cancer. An installment of The Oncology Grand Rounds series, which was published in the Journal of Clinical Oncology, applied the results of a key study to this clinical context of case presentations.

The first case presentation focused on a 54-year-old postmenopausal woman with grade 2 HER2-negative infiltrating ductal cancer; a total of 95%, 40%, and 26% of tumor nuclei were positive for estrogen receptor, progesterone receptor, and Ki67, respectively. The investigators also presented the case of a 55-year-old postmenopausal woman with the same diagnosis; however, in this patient, estrogen receptor, progesterone receptor, and Ki67 positivity were reported in 90%, 80%, and 15% of tumor nuclei, respectively.

In brief, the monarchE trial evaluated whether abemaciclib may be added to adjuvant endocrine therapy in patients with high-risk hormone receptor–positive breast cancer. Based on the results, adjuvant abemaciclib therapy was approved by the U.S. Food and Drug Administration (FDA) for the treatment of those with a Ki67 expression level of at least 20%.

“Both [of] these cases meet eligibility for adjuvant abemaciclib on the basis of the monarchE results, although [the second case] does not per the FDA approval,” the investigators concluded. “Informed discussion with our patients with node-positive, hormone receptor–positive disease regarding adjuvant abemaciclib is warranted for any who meet eligibility criteria for monarchE.”

Disclosure: For full disclosures of the study authors, visit

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