Identification and Management of Medical Comorbidities in Patients With HR+/HER2– Metastatic Breast Cancer Treated With CDK4/6 Inhibitors: Literature Review and Recommendations From Experts in Spain Opinion

Approximately one-third of patients with breast cancer have comorbidities at the time of their diagnosis. Recommendations for managing metastatic breast cancer are usually based on the results of clinical trials, which often limit patients with comorbidities. However, comorbidities greatly influence the quality of life, patient survival rate and treatment choice, particularly in older patients. The objective of this review was to identify clinically relevant comorbidities in patients with metastatic breast cancer, analyze the clinical approach to the treatment of these comorbidities, and propose recommendations from experts. An expert panel of eight medical oncologists identified seven therapeutic areas associated with the most relevant comorbidities in metastatic breast cancer: cardiovascular, gastrointestinal, endocrine/metabolic, renal, geriatric, psychological, and pain related. A clinical specialist from each therapeutic area specific to the relevant comorbidities (n = 8) joined the panel of experts (n = 8) to provide guidance on the appropriate management of these comorbidities. The specific comorbidities analyzed were hypertension, atrial fibrillation, venous thromboembolism, obesity, diabetes mellitus, cancer cachexia, chronic kidney disease, age-related disorders, arthritis, and fibromyalgia. In most cases, patients with metastatic breast cancer and medical comorbidities are polymedicated and/or vulnerable to toxicity. The oncologists provided recommendations on initial assessment and monitoring, follow-up recommendations, and warning signs and symptoms for referral to corresponding specialists based on their experience. The panel of experts also explored clinical scenarios related to each comorbidity and recommended a preferred CDK4/6 inhibitor based on available evidence regarding drug–drug interactions and potential for toxicity.