Evaluation of drug-drug interactions among patients with metastatic prostate cancer in routine care.

Abstract

111 Background: Prostate cancer often occurs in an elderly population, at higher risk of drug-drug interactions (DDIs). There is a medical need to increase the knowledge of DDI prevalence and their severity among patients coming from routine care. This study used a prospective approach with the aim to quantify and describe DDIs in medical prescription of prostate cancer treatments. Methods: DDIs were assessed from two perspectives: 1) “real DDI” between the patient’s comedications and the actual anti-cancer agent prescribed; 2) “modelized DDI” between the patient’s comedications and drugs that have proven activity in metastatic endocrine sensitive prostate cancer (MESPC) or castrate resistant prostate cancer (CRPC) settings with positive phase 3 trial and gained EMA approval. French national thesaurus, Micromedex software and complementary manual analysis by pharmacist were used to identified DDIs. Clinical relevance of DDIs was scored using the validated scale of Hatoum. Results: A total of 91 patients were included, 15% of whom were participating in a clinical trial. Some imbalances were observed between patients from clinical trial and routine care (age, ECOG, MESPC/MCRPC). The median number of comedications used per patient was 6 [1-16]. Among real DDI, Enzalutamide was the anticancer agent with the higher risk of interaction (18-54% of patients). In modelized DDI, Enzalutamide and Apalutamide were the two most risky drugs (35-76% and 22-73% depending on Micromedex or Thesaurus analyze). Not all DDIs discovered were clinically significant according to Hatoum scale. Conclusions: DDIs are frequents, according to Micromedex and National Thesaurus tools but pharmacist and physician advices are essentials to determine their potential impacts.