Aim: Abiraterone acetate is approved for the treatment of metastatic prostate cancer. At the currently used fixed dose of 1000 mg once daily in modified fasting state, 40% of patients do not reach the efficacy threshold of a minimum plasma concentration (Cmin) ≥ 8.4 ng/mL and are thereby at risk of decreased treatment efficacy. This study aims to evaluate whether pharmacokinetically (PK) guided abiraterone acetate dosing with a food intervention is feasible and results in an increased percentage of patients with concentrations above the target.
Methods: Patients starting regular treatment with abiraterone acetate in modified fasting state were included. Pharmacokinetic analysis was performed 4, 8 and 12 weeks after start of treatment and every 12 weeks thereafter. In case of Cmin < 8.4 ng/mL and acceptable toxicity, a PK-guided intervention was recommended. The first step was concomitant intake of abiraterone acetate with a light meal or a snack.
Results: In total, 32 evaluable patients were included, of which 20 patients (63%) had a Cmin < 8.4 ng/mL at a certain time point during treatment. These patients were recommended to take abiraterone acetate concomitantly with food, after which Cmin increased from 6.9 ng/mL to 27 ng/mL (p < 0.001) without additional toxicities. This intervention led to adequate exposure in 28 patients (87.5%).
Conclusion: Therapeutic drug monitoring of abiraterone was applied in clinical practice and proved to be feasible. Concomitant intake with food resulted in a significant increase in Cmin and offers a cost-neutral opportunity to optimise exposure in patients with low Cmin.
Keywords: abiraterone acetate; drug monitoring; pharmacokinetics; prostate cancer.
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