The burden of polypharmacy and drug-drug interactions in older cancer patients treated with immunotherapy.

INTRODUCTION Polypharmacy is a common problem in older cancer patients, although the data about polypharmacy and potentially inappropriate prescription practices is limited in patients treated with immune checkpoint inhibitors (ICIs). Therefore, we aimed to evaluate the polypharmacy frequency and drug-drug interactions in older cancer patients (≥65 years) treated with ICIs. METHODS A total of 70 geriatric patients with advanced cancer were included. The polypharmacy was defined as regular use of 5 or more drugs. The START/STOPP Criteria Version 2 was used for the potentially inappropriate medications (PIM) and potential prescription omissions (PPO). The Medscape Drug Interaction Checker was used for potential drug-drug interactions. RESULTS The patients had a median of 6 regular drugs, and polypharmacy was present in 77.1%. The polypharmacy risk was significantly increased in patients over 75 years of age (p = 0.028) and with opioid use (p = 0.048). The 50% of patients had category D or X interactions. Patients with higher Charlson Comorbidity Index had significantly increased risk for drug interactions (CCI ≤10 vs. >10, p = 0.017). The PIMs were present in 44.3% and the PPOs in 68.6% of the patients. While the overall survival and immune related adverse events were similar according to polypharmacy, in patients using seven or more drugs, the acute kidney injury risk was increased (HR: 4.667, p = 0.038). CONCLUSION In this study, we observed a high rate of polypharmacy and inappropriate prescription practices in ICI-treated patients. These issues pointed out the need for improved general medical care and attention for better comedication management in ICI-treated patients.