Skill Checkup: A Menopausal Woman With a Lump in Her Right Breast

Pavani Chalasani, MD, MPH

Disclosures

January 18, 2022

In October 2021, the US Food and Drug Administration issued its first approval for a CDK 4/6 inhibitor plus endocrine therapy for the adjuvant treatment of patients with node-positive, high-risk HR-positive, HER2-negative early breast cancer. Abemaciclib was approved in combination with either tamoxifen or an aromatase inhibitor in eligible patients with a Ki-67 level of 20% or higher on the basis of findings from the monarchE trial. The investigators compared the abemaciclib combination with endocrine therapy alone and found that the combination was associated with a 25% relative risk reduction in invasive disease–free survival (P = .0096; hazard ratio, 0.75; 95% CI, 0.60-0.93). At 2 years, the rate of invasive disease–free survival was 92.2% in patients who received the abemaciclib combination compared with 88.7% in those who received endocrine therapy alone. As expected, the safety profile of the combination was associated with a higher incidence of adverse effects (eg, diarrhea, neutropenia, interstitial pneumonitis) compared with endocrine monotherapy. Nevertheless, with appropriate management, adverse effects appeared to neither interfere with nor reduce the survival benefits of treatment.

These results were heralded by many breast cancer experts as the first meaningful advance in the adjuvant treatment of early-stage, high-risk disease in two decades.

All of the other classes of agents, such as antiestrogens (eg, tamoxifen), estrogen receptor antagonists (eg, fulvestrant), and selective estrogen receptor modulators (eg, raloxifene) are broadly considered endocrine therapies, which are appropriate but perhaps insufficient based on the new data from monarchE.

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