CDK4/6 Inhibitors Are Game Changers in HR+/HER2- Advanced Breast Cancer

PTCE would like to acknowledge Lilly USA, LLC and Novartis Pharmaceuticals Corporation for their generous support of pharmacist education.

In a live, virtual symposium, 2 expert speakers discussed hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) breast cancer, which accounts for approximately two- thirds of more than 279,000 breast cancer diagnoses annually in the United States. The program, HR+/HER2- Advanced Breast Cancer Treatment With CDK4/6 Inhibitors: Improving Care for Patients, first addressed appropriate use of endocrine and cyclin-dependent kinase (CDK) 4/6 inhibitor therapy in patients with HR+/ HER2- breast cancer and the evolving guideline recommendations. Strategies for pharmacists to communicate with patients receiving treatment with a CDK4/6 inhibitor to optimize care and promote best outcomes were also discussed.

Sandra Cuellar, PharmD, BCOP, dove right into the management of HR+/HER2- advanced breast cancer by explaining that chemotherapy is only recommended in certain patients, such as those with visceral metastases or progression on multiple lines of endocrine therapy. She explained initial therapy may include endocrine therapy with an aromatase inhibitor or fulvestrant combined with CDK4/6 inhibitor-targeted therapy with abemaciclib, palbociclib, ribociclib, or endocrine therapy alone. Dr Cuellar noted the addition of CDK4/6 inhibitors to standard endocrine therapy in both pre- and post- menopausal women improves progression-free survival. She highlighted that treatment selection should consider patient-specific factors such as previous therapies and disease-free interval.

Dr Cuellar then focused on second-line therapy options shown to improve progression-free survival, including fulvestrant combined with a CDK4/6 inhibitor or PIK3CA inhibitor. She ended her session by reviewing further treatment options, future directions of therapy, and the role of biomarker testing.

Danielle Roman, PharmD, BCOP, began her session by explaining how patient awareness and education are key components of managing potential medication adverse effects. She emphasized that early intervention of adverse effects may reduce symptoms and help improve medication adherence. Dr Roman provided great clinical pearls for management of the following common clinical adverse effects:

• Neutropenia
• Diarrhea
• Hepatotoxicity
• Nausea/vomiting
• Fatigue
• Alopecia

She highlighted the FDA warning issued in September 2019 for the risk of intersti- tial lung disease with CDK4/6 inhibitors and encouraged monitoring for hypoxia, cough, and dyspnea. She also touched on drug-specific pearls, such as QTc prolongation with ribociclib and diarrhea with abemaciclib. Management of drug interactions, particularly those mediated by CYP3A, were reviewed for all CDK4/6 inhibitors. Dr Roman wrapped up the symposium by describing challenges with managing patients on CDK4/6 inhibitors, including monitoring patient treatment cycles, ensuring appropriate laboratory monitoring at timely intervals, patient adherence to therapy, and optimal communication among the multidisciplinary team members.