Recommendations for cyclin‑dependent kinase 4/6 inhibitor treatments in the context of co‑morbidity and drug interactions (Review).

Breast cancer is most frequently diagnosed among women aged 65-74 years and the prevalence of comorbidities in elderly patients with breast cancer is 32.2%. In addition, polypharmacy is quite common in these patients. Understanding the interaction between breast cancer treatment modalities and comorbidities is important, particularly in elderly patients, as comorbidities affect the choice of appropriate treatment and are independent risk factors for survival. A total of three oral cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i), palbociclib, ribociclib and abemaciclib, notably prolonged progression-free survival when combined with endocrine therapy (ET), compared with ET alone in patients with advanced breast cancer (ABC). The present review article therefore addressed the safety, tolerability and toxicity of CDK4/6i treatment in ABC management, compiled real-world data on how multiple clinical and pharmacological features may affect the choice of these drugs and provided practical recommendations for clinical approaches. Before starting treatment with CDK4/6i drugs, all ongoing medical conditions should be inventorized and re-graded, and examination should be performed for any additional disease that the patient may not be aware of. It is also important to obtain a detailed history of concomitant drugs, including prescription and over-the-counter drugs, vitamins, supplements and herbal products. In addition, patients should be advised to consult their oncologist before starting any new medication.