High prevalence of potential drug-drug interactions in patients with castration-resistant prostate cancer treated with abiraterone acetate

Clinical implications of the Drug-Drug Interaction in Cancer Patients treated with innovative oncological treatments

In the last two-decades, innovative drugs have revolutionized cancer treatments, demonstrating a significant improvement in overall survival. These drugs may present several pharmacokinetics interactions with non-oncological drugs, and vice versa, and, non-oncological drugs can modify oncological treatment outcome both with pharmacokinetic interaction and with an "off-target impact" on the tumor microenvironment or on the peripheral immune response. It's supposed that the presence of a drug-drug interaction (DDI) is associated with an increased risk of reduced anti-tumor effects or severe toxicities. However, clinical evidence that correlate the DDI presence with outcome are few, and results are difficult to compare because of difference in data collection and heterogeneous population. This review reports all the clinical evidence about DDI to provide an easy-to-use guide for DDI management and dose adjustment in solid tumors treated with inhibitors of the cyclin-dependent kinases CDK4-6, Antibody-drug conjugates, Poly ADPribose polymerase inhibitors, androgen-receptor targeted agents, or immunecheckpoints inhibitors.

Impact of Comorbidities and Drug Interactions in Patients With Metastatic Castration-Resistant Prostate Cancer Receiving Androgen Receptor Pathway Inhibitors

PURPOSE

Androgen receptor pathway inhibitors (ARPIs) are widely prescribed in metastatic castration-resistant prostate cancer (mCRPC). Real-world frequencies and potential impacts of comorbidities and concomitant medication (conmed) interactions with ARPIs are not well described.

METHODS

Patients receiving ARPIs for mCRPC were identified from the electronic Prostate Cancer Australian Database (ePAD). Demographics, clinicopathologic characteristics, and outcome data were extracted. Conmeds and comorbidities were collected from medical records. Potential interacting comorbidities were defined from trial and post-trial data. Clinically significant drug-drug interactions (DDIs) were identified using UpToDate Lexicomp and Stockley's databases. Patient characteristics, comorbidity interactions, DDIs, and outcomes were analyzed.

RESULTS

Two hundred thirty-five patients received first- or second-line ARPIs for mCRPC from 2012 to 2021, with a median follow-up of 27 months. One hundred sixteen received abiraterone acetate (AAP) and 135 received enzalutamide (ENZ). The median age was 74 years, and the median number of conmeds was 4. Clinically significant DDIs occurred in 55 (47%) AAP patients and 90 (67%) ENZ patients. Only 5% of DDIs were predicted to affect ARPI pharmacokinetics (PK) or pharmacodynamics, whereas 95% were predicted to impact conmed PK or increase toxicity risk. In patients receiving ENZ, DDIs were associated with lower PSA50 (50% v 74%, P = .04) and poorer overall survival (28 v 45 months, P = .04), although statistical significance was not maintained on multivariate analysis. No significant survival differences were seen with DDIs in patients receiving AAP. Potential interactions between comorbidities and ARPI were present in 72% on AAP and 14% on ENZ with no significant associated survival differences.

CONCLUSION

DDIs and drug-comorbidity interactions in real-world patients receiving ARPIs for mCRPC are common and may affect outcomes. Ongoing clinician education regarding DDIs is necessary to optimize patient outcomes.

Hospitalizations Among Veterans Treated for Metastatic Prostate Cancer With Abiraterone or Enzalutamide

BACKGROUND

Abiraterone and enzalutamide are second generation androgen receptor pathway inhibitors (ARPIs) used to treat advanced or metastatic prostate cancer. Without head-to-head comparative studies identifying 1 agent as preferred initial therapy, physician preferences guide initial ARPI choice. This study compares hospitalizations among patients treated initially with abiraterone versus enzalutamide.

PATIENTS AND METHODS

United States veterans treated with abiraterone or enzalutamide between May 13, 2011 and December 31, 2019; then compared hospitalization rate during first treatment with ARPI in the Veterans Healthcare Administration. Baseline incidence rate of hospitalization was determined from data 1 year prior to ARPI. Incidence Rate Difference (IRD) was calculated using χ2 test and difference in IRD using Poisson Regression.

RESULTS

19,775 veterans were identified; 13,527 (68.4%) were initially treated with abiraterone and 6248 (31.6%) initially with enzalutamide. The enzalutamide cohort was older (75.8 vs. 74.5 years, P < .001) and had higher baseline comorbidities at ARPI initiation (4.4 vs. 4.0, P < .001). Patients were treated with enzalutamide longer than abiraterone (median 9.0 vs. 8.0 months, P < .001). Total hospitalizations increased from 465 per 1000 person-years in the year prior to treatment with abiraterone to 567 during treatment. Total hospitalizations increased from 417 per 1000 person-years in the year prior to treatment with enzalutamide to 430 during treatment. Total rate of hospitalization increased 22% for abiraterone compared to a 3% increase for enzalutamide in the 12 months after ARPI initiation (P < .0001). Abiraterone was associated with greater increase in rates of acute heart failure, atrial fibrillation, acute kidney injury, urinary tract infections, sepsis, and pneumonia.

CONCLUSION

By comparing the rate of hospitalization before vs. during treatment, real world analyses identified a 22% versus 3% increase in hospitalizations with abiraterone compared to enzalutamide respectively, despite being used in a younger population with less comorbid disease. Abiraterone was also associated with higher risk of infections, a novel finding.

A new method to quantify the effect of co-medication on the efficacy of abiraterone in metastatic castration-resistant prostate cancer patients

Background and Objective: Patients with metastatic castration-resistant prostate cancer (mCRPC) treated with abiraterone acetate (AA) have co-morbidities treated with different drugs. The aim was to quantify the potential effect of co-medications on AA treatment duration (TD) and overall survival (OS). Methods: A new parameter, called "individual drug score" (IDS) was calculated by summing the "drug score"-s (DS) of all co-medications for each patient. The DS was determined by quantifying the effect of a given co-drug on enzymes involved in steroidogenesis and metabolism of AA. The correlation between log (IDS) and TD was tested by non-linear curve fit. Kaplan-Meier method and multivariate Cox regression was used for analysis of TD and OS. Results: The IDS and TD of AA+prednisolone showed a dose-response correlation (n = 166). Patients with high IDS had significantly longer TD and OS (p <0.001). In multivariate analysis IDS proved to be an independent marker of TD and OS. The same analysis was performed in a separate group of 81 patients receiving AA+dexamethasone treatment. The previously observed relationships were observed again between IDS and TD or OS. After combining the AA+prednisolone and AA+dexamethasone groups, analysis of the IDS composition showed that patients in the high IDS group not only used more drugs (p <0.001), but their drugs also had a higher mean DS (p = 0.001). Conclusion: The more co-drugs with high DS, the longer the duration of AA treatment and OS, emphasizing the need for careful co-medication planning in patients with mCRPC treated with AA. It is recommended that, where possible, co-medication should be modified to minimize the number of drugs with negative DS and increase the number of drugs with high DS. Our new model can presumably be adapted to other drugs and other cancer types (or other diseases).

Effect of Dexamethasone on Abiraterone Pharmacokinetics in Mice: Determined by LC/MS Analysis

Background: Abiraterone acetate is a cytochrome P450 17A1 (CYP17A1) inhibitor that is indicated for use in both castration-resistant and castration-sensitive prostate cancer patients. To manage the mineralocorticoid effects of CYP17A1 inhibition, a glucocorticoid such as dexamethasone is co-administered with abiraterone. The goal of the present study was to understand the effect of dexamethasone on the disposition of abiraterone. Methods: Adult male CD-1 mice were treated with either dexamethasone (80 mg/kg/day) or vehicle for three consecutive days, followed by the administration of a single dose of abiraterone acetate (180 mg/kg) as an oral gavage. Blood samples were collected by tail bleeding at timepoints between 0 to 24 h. Subsequently, abiraterone was extracted from the mouse serum using a neutral pH condition and serum abiraterone levels were determined using a liquid chromatography–mass spectrometry assay. Results: Our results demonstrated that dexamethasone lowered the maximum plasma concentration and area under the curve parameters by approximately five- and ten-fold, respectively. Similar effects were also observed on the plasma half-life and oral clearance parameters. This is the first report of dexamethasone effect on abiraterone disposition in vivo. Conclusions: We conclude that dexamethasone has the potential to reduce the plasma abiraterone level and thus compromise its CYP17A1 inhibitory ability in the procancerous androgen biosynthesis pathway. Thus, use of a higher abiraterone dose may be warranted when used alongside dexamethasone.

New Oral Antitumor Drugs and Medication Safety in Uro-Oncology: Implications for Clinical Practice Based on a Subgroup Analysis of the AMBORA Trial

Oral antitumor therapeutics (OAT) bear a high risk for medication errors, e.g., due to drug–drug or drug–food interactions or incorrect drug intake. Advanced age, organ insufficiencies, and polymedication are putting uro-oncological patients at an even larger risk. This analysis sets out to (1) investigate the frequency and relevance of medication errors in patients with prostate cancer or renal cell carcinoma treated with OAT and (2) compile recommendations for clinical practice. This post-hoc subgroup analysis used data collected in the randomized AMBORA trial (2017–2020; DRKS00013271). Clinical pharmacologists/pharmacists conducted advanced medication reviews over 12 weeks after initiation of a new oral regimen and assessed the complete medication process for drug–related problems. Medication errors related to either the OAT, prescribed or prescription-free concomitant medication, or food were classified regarding cause and severity. We identified 67 medication errors in 38 patients within the complete medication within 12 weeks. Thereof, 55% were detected at therapy initiation, 27% were caused by the patients, and 25% were drug–drug or drug–food interactions. Problem-prone issues are summarized in a ‘medication safety table’ to provide recommendations for clinical practice in uro-oncology. Tailored strategies including intensified care by clinical pharmacologists/pharmacists should be implemented in clinical practice to improve medication safety.

The Prevalence of Polypharmacy and Potential Drug-Drug Interactions among Iranian Cancer Patients: which Patients Were at Risk?

INTRODUCTION

Drug-Drug interactions (DDIs) are one of the considerable consequences of polypharmacy. Due to the influence of polypharmacy and drug interactions on cancer treatment and patients` health outcomes, the present study aimed to determine the prevalence of polypharmacy and potential DDIs among adult cancer patients in Kerman province, southeast of Iran.

METHODS

In this cross-sectional study, 315 cancer patients who referred to Kerman city oncology clinics were assessed in 2018. Data were collected through face-to-face interviews and medical charts were reviewed. Polypharmacy was defined as the use of at least five drugs simultaneously. Potential DDIs were checked using the "Drugs.com" online database. A bivariable and a multivariable logistic regression were used to determine the associated factors of outcome variables, polypharmacy status and potential DDI in SPSS software version 23.

RESULTS

Of 315 cancer patients, 191 patients (60.6%; 95% CI:54.9, 66) used at least five drugs during chemotherapy courses. The prevalence of potential DDIs was 59.6% (n = 140, 95% CI: 53.6-66.0. Experience co-morbid diseases (OR:6.60; 95%CI: 3.82, 11.42; P-value ≤0.0001), and positive metastatic status (OR:2.80; 95%CI: 1.62, 4.82; P-value ≤0.0001) could predict the polypharmacy during chemotherapy courses. Patients who suffered gastrointestinal cancers (OR:5.55; 95%CI: 2.26, 13.62; P-value ≤0.0001) and the number of prescribed or Over The Counter (OTC) drugs (OR:1.29; 95%CI: 1.12, 1.48; P-value <0.0001) predicted the occurrence of potential DDIs among cancer patients.

CONCLUSION

Regarding the high prevalence of polypharmacy and potential drug interactions among Iranian cancer patients during chemotherapy courses, it is advisable for physicians, nurses, and pharmacists to be vigilant to improve prescribing patterns. In addition, with intensive monitoring, alternative treatment strategies can be replaced.

Potential and real drug interactions in patients treated with abiraterone or enzalutamide in clinical practice

BACKGROUND

Abiraterone and enzalutamide, androgen receptor pathway inhibitors (ARPI) for the treatment of metastatic castration-resistant prostate cancer (mCRPC), are at high risk of potential drug interactions (PDIs). We aimed to describe PDIs and their management, and triggered adverse events (AEs) in clinical practice.

METHODS

We conducted a cross-sectional study in mCRPC patients who started treatment with abiraterone or enzalutamide in a university hospital between August 1st, 2016 and July 31st, 2020. Lexicomp® was used to identify and analyze PDIs, and the clinical records to assess their management and the occurrence of AEs.

RESULTS

We included 173 patients: 36.8% and 93.0% of patients treated with abiraterone and enzalutamide, respectively, had at least 1 PDI. Globally, 6.3% of PDIs had X-risk (contraindication due to high probability of AE). Treatment was modified in 9.2% of patients and 9.8% suffered AEs due to PDIs. Factors associated with a higher risk of PDIs were polypharmacy (OR=41.0, p=0.003) and treatment with enzalutamide (OR=128.26, p< 0.001).

CONCLUSIONS

At least two-thirds of patients treated with ARPI suffered a PDI. Overall, abiraterone would have a more favorable PDI profile. Knowing these interaction profiles may be helpful to develop a more efficient therapeutic follow-up and to select the safest treatment.

Pharmacokinetic Drug-Drug Interaction of Apalutamide, Part 1: Clinical Studies in Healthy Men and Patients with Castration-Resistant Prostate Cancer

BACKGROUND AND OBJECTIVES

Two phase I studies assessed the drug-drug interaction potential of apalutamide as a substrate and perpetrator.

METHODS

Study A randomized 45 healthy men to single-dose apalutamide 240 mg alone or with strong inhibitors of cytochrome P450 (CYP)3A4 (itraconazole) or CYP2C8 (gemfibrozil). In study B, 23 patients with castration-resistant prostate cancer received probes for CYP3A4 (midazolam), CYP2C9 (warfarin), CYP2C19 (omeprazole), and CYP2C8 (pioglitazone), and transporter substrates for P-glycoprotein (P-gp) (fexofenadine) and breast cancer resistance protein (BCRP)/organic anion transporting polypeptide (OATP) 1B1 (rosuvastatin) at baseline and after repeat once-daily administration of apalutamide 240 mg to steady state.

RESULTS

Systemic exposure (area under the plasma concentration-time curve) to single-dose apalutamide increased 68% with gemfibrozil but was relatively unchanged with itraconazole (study A). Apalutamide reduced systemic exposure to midazolam ↓92%, omeprazole ↓85%, S-warfarin ↓46%, fexofenadine ↓30%, rosuvastatin ↓41%, and pioglitazone ↓18% (study B). After a single dose, apalutamide is predominantly metabolized by CYP2C8, and less by CYP3A4.

CONCLUSIONS

Co-administration of apalutamide with CYP3A4, CYP2C19, CYP2C9, P-gp, BCRP or OATP1B1 substrates may cause loss of activity for these medications. Therefore, appropriate mitigation strategies are recommended.

Recognition, Prevention, and Management of Arrhythmias and Autonomic Disorders in Cardio-Oncology: A Scientific Statement From the American Heart Association

With the advent of novel cancer therapeutics and improved screening, more patients are surviving a cancer diagnosis or living longer with advanced disease. Many of these treatments have associated cardiovascular toxicities that can manifest in both an acute and a delayed fashion. Arrhythmias are an increasingly identified complication with unique management challenges in the cancer population. The purpose of this scientific statement is to summarize the current state of knowledge regarding arrhythmia identification and treatment in patients with cancer. Atrial tachyarrhythmias, particularly atrial fibrillation, are most common, but ventricular arrhythmias, including those related to treatment-induced QT prolongation, and bradyarrhythmias can also occur. Despite increased recognition, dedicated prospective studies evaluating true incidence are lacking. Moreover, few studies have addressed appropriate prevention and treatment strategies. As such, this scientific statement serves to mobilize the cardio-oncology, electrophysiology, and oncology communities to develop clinical and scientific collaborations that will improve the care of patients with cancer who have arrhythmias.

Clinical Approach to Cardiovascular Toxicity of Oral Antineoplastic Agents: JACC State-of-the-Art Review

Precision medicine has ushered in a new era of targeted treatments for numerous malignancies, leading to improvements in overall survival. Unlike traditional chemotherapy, many molecular targeted antineoplastic agents are available in oral formulation, leading to enhanced patient convenience and a perception of reduced risk of adverse effects. Although oral antineoplastic agents are generally well-tolerated, cardiovascular toxicities are being reported with increasing frequency in part due to U.S. Food and Drug Administration and manufacturer recommended cardiac monitoring. Monitoring strategies have focused on left ventricular dysfunction, hypertension, and QT prolongation/arrhythmias. Given the rapid pace of development and availability of new oral antineoplastic agents, the purpose of this review is to provide clinicians with an up-to-date practical approach to monitoring and management of cardiovascular toxicities with the aim of improving overall outcomes for patients with cancer.

Mortality and Hospitalization Risk Following Oral Androgen Signaling Inhibitors Among Men with Advanced Prostate Cancer by Pre-existing Cardiovascular Comorbidities

BACKGROUND

Elderly patients (≥65yr) with advanced prostate cancer and cardiovascular disease (CVD) conditions are often excluded from clinical trials of abiraterone acetate (AA) or enzalutamide (ENZ). Consequently, little is known about the effects of these medications on these vulnerable patients.

OBJECTIVE

To assess the short-term outcomes of AA and ENZ in patients with pre-existing CVDs.

DESIGN, SETTING, AND PARTICIPANTS

A population-based retrospective study. The Surveillance, Epidemiology, and End Results-Medicare-linked database was used to identify prostate cancer patients using AA or ENZ.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was 6-mo all-cause mortality, analyzed using modified Poisson regression modeling of relative risk (RR) adjusted for confounders and comorbidities.

RESULTS AND LIMITATIONS

Among eligible patients (2845 with AA and 1031 with ENZ), 67% had at least one pre-existing CVD. Compared with those without pre-existing CVDs, having one to two pre-existing CVDs was associated with 16% higher 6-mo mortality (RR=1.16, 95% confidence interval [CI]: 1.00-1.36), and the risk increased further among those having three or more CVDs (RR=1.56, 95% CI: 1.29-1.88). Most of the differences in survival of patients with pre-existing CVD condition occurred within the first 6mo of treatment.

CONCLUSIONS

After treatment with AA or ENZ, elderly prostate cancer patients with pre-existing CVDs experienced higher short-term mortality than otherwise similar patients without CVDs. Mortality associated with CVDs did not depend on having received AA versus ENZ.

PATIENT SUMMARY

Patients with pre-existing cardiovascular diseases (CVDs) experienced higher short-term mortality after abiraterone acetate or enzalutamide than those without pre-existing CVDs. It is recommended that a multidisciplinary team, including a cardiologist, evaluate patients having pre-existing CVDs in the process of making treatment decisions and monitoring potential side effects.

Management of anticoagulation in patients with metastatic castration-resistant prostate cancer receiving abiraterone + prednisone

PURPOSE

Abiraterone has been proven to be an effective agent used in the management of metastatic castration-resistant prostate cancer, significantly improving overall and progression-free survival. Due to the pharmacodynamic and pharmacokinetic properties of abiraterone, concurrent use with anticoagulation may pose a challenge for clinicians. Thrombosis within the cancer setting continues to increase patient mortality; therefore, appropriate anticoagulation through the use of a management algorithm can reduce adverse events and increase quality of life.

METHODS

A review of the literature was preformed by a medical oncologist, haematologist and pharmacists to identify relevant randomized controlled trials, meta-analyses and retrospective studies. Major society guidelines were reviewed to further aid in developing the anticoagulation protocol for non-valvular atrial fibrillation and venous thromboembolism within this patient population. After reviewing the literature, a clinical framework was designed to aid clinicians in the management of those patients receiving abiraterone concurrently with an anticoagulant.

RESULTS

In this review, we describe the potential interactions between abiraterone and various anticoagulants and provide management strategies based on the most recent literature for atrial fibrillation, venous thromboembolism and mechanical heart valves to avoid potential drug-drug interactions.

CONCLUSION

Abiraterone therapy has become a mainstay of the management of advanced prostate cancer and is often used over prolonged years. In this review, we have summarized a framework of how to use abiraterone in men with prostate cancer on anticoagulants. Evidence available to date suggests that patients with an indication for anticoagulation such as atrial fibrillation, venous thromboembolism and mechanical heart valves can be treated safely with abiraterone in the appropriate setting, with appropriate monitoring.

Clinical pharmacology of oncology agents in older adults: A comprehensive review of how chronologic and functional age can influence treatment-related effects

Unique challenges exist when managing older adults with cancer. Associations between cancer and age-related physiologic changes have a direct impact on pharmacokinetics and pharmacodynamics of cancer therapies and can affect drug dosing, dose intensity, efficacy, safety and quality of life. The breadth and depth of these issues, however, have not been fully evaluated because the majority of clinical trials have focused on a younger and healthier population. As a consequence, little information is available to support clinicians in making evidence-based decisions regarding treatment with cancer therapies in older adults, especially those over age 75. Prior clinical pharmacology reviews summarized the literature on how age-related physiologic changes can influence and affect conventional and targeted anti-cancer treatments. Our article provides an updated review with expanded information that includes small molecule kinase inhibitors, monoclonal antibodies, immunotherapies, hormonal, conventional, and miscellaneous agents. Additionally, our article integrates how functional age, determined by the geriatric assessment (GA), can also influence treatment-related effects and health outcomes. Broadening cancer therapy trials to capture not only chronologic age but also functional age would allow clinicians to better identify subsets of older adults who benefit from treatment versus those most vulnerable to morbidity and/or mortality.

The prevalence of major drug-drug interactions in older adults with cancer and the role of clinical decision support software

OBJECTIVES

Drug-drug interactions (DDIs) represent an escalating concern for older adults attributed to polypharmacy, multi-morbidity and organ dysfunction. Few studies have evaluated the prevalence of major DDIs and the variability between DDI detection software which confuses management.

MATERIALS AND METHODS

Prevalence of major DDIs was examined as a secondary analysis of outpatients aged ≥65 years. Demographic and clinical information was collected from electronic health records including age, sex, race, cancer type, comorbidities, and medications. All DDIs were screened by a clinical pharmacist using Lexi-Interact® and Micromedex®. Major DDIs were defined as Lexi-Interact® category D or X and/or Micromedex® category major or contraindication. Summary statistics of patient characteristics and DDIs were computed.

RESULTS

Our cohort included 142 patients (mean age, 77.7 years; 56% women, 73% Caucasian). The mean medications was 9.8 including 6.7 prescriptions, 2.6 non-prescriptions, and 0.5 herbals. Lexi-Interact® identified 310 major DDIs in 69% of patients (n = 98) with an average of 2.2 DDIs per patient. Micromedex® identified 315 major DDIs in 61% of patients (n = 87) with an average of 2.2 DDIs per patient. DDIs mostly involved opioids, antiplatelets, electrolyte supplements, antiemetics, and antidepressants. Variability existed with the severity rating reporting of the clinical decision support software.

CONCLUSIONS

There was a high prevalence of major DDIs in older adults with cancer. Utilizing clinical decision support software was beneficial for detecting DDIs however, variability existed with severity reporting. Future studies need to identify the relevant DDIs with clinical implications in order to optimize medication safety in this population.

Drug-drug interaction potential in men treated with enzalutamide: Mind the gap

AIMS

Metastatic castration-resistant prostate cancer (mCRPC) patients are generally older patients with several co-morbidities and are therefore at increased risk of complications due to drug-drug interactions (DDIs). We assessed the prevalence of potential DDIs in a cohort of mCRPC patients treated with enzalutamide.

METHODS

We conducted a retrospective review of pharmacy records to retrieve individual drug histories of mCRPC patients who started enzalutamide therapy in a tertiary care setting. Potential DDIs were analysed using two international drug interaction compendia: Lexicomp^® and Micromedex^® , and the Dutch drug database. Two potential pharmacodynamic DDIs were analysed.

RESULTS

A total of 105 records were evaluated for potential DDIs with enzalutamide. Of 205 different co-medications, 56 were flagged by at least one of the three compendia: Lexicomp, Micromedex and the Dutch drug database flagged for potential DDIs in 85%, 54% and 32%, respectively. Eighty-five per cent of DDIs were classified as major. The median number of co-medications per patient was 11 (range 1-26). The median (range) number of interactions per patient was 4 (0-10), 1 (0-5) and 0 (0-2) for Lexicomp, Micromedex and the Dutch drug database, respectively. In 23% and 45% of all patients, a potential DDI was found with PPIs and CNS depressants, respectively.

CONCLUSIONS

A high prevalence of potential DDIs was found. The inclusion and grading of potential DDIs was highly variable between the three drug interaction compendia. Physicians, nurses and pharmacists should be aware of this potential problem, which might require intensive monitoring or alternative treatment strategies to prevent suboptimal treatment of the co-morbidities in patients treated with enzalutamide.

Potential drug-drug interactions with abiraterone in metastatic castration-resistant prostate cancer patients: a prevalence study in France

PURPOSE

Abiraterone acetate combined with prednisone improves survival in metastatic castration-resistant prostate cancer (mCRPC) patients. This oral anticancer agent may result in drug-drug interactions (DDI). We aimed to evaluate the prevalence of DDI with abiraterone and the possible determinants for the occurrence of these DDI.

METHODS

We performed a single centre retrospective review from electronic medical records of mCRPC patients treated with abiraterone from 2011 to 2015. Potential DDI with abiraterone were identified using Micromedex and were categorized by a 4-point scale severity.

RESULTS

Seventy-two out of ninety-five mCRPC pts (median age: 77 years [68-82]) had comorbidities. The median number of drugs used per patient was 7 [5-9]. 66 potential DDI with abiraterone were detected in 49 patients (52%): 39 and 61% were classified as major and moderate DDI, respectively. In the univariate analysis, pain (p < 0.0001), hypo-albuminemia (p = 0.032), and higher ECOG performance status (PS) (p = 0.013) were significantly associated with a higher risk of DDI with abiraterone. Pain (p < 0.0001) and PS (p = 0.018) remained significant in the multivariate analysis.

CONCLUSIONS

Polypharmacy is an issue among mCRPC patients. In our study, half of the patients have potential DDI with abiraterone. Patients with pain and poor PS are at higher risk of DDI with abiraterone. A medication review by a pharmacist is of crucial importance to prevent DDI with abiraterone.