Recommended Treatment Regimen for Zytiga (Abiraterone) in Metastatic Castration-Resistant Prostate Cancer
For patients with metastatic castration-resistant prostate cancer (mCRPC), the recommended treatment regimen for Zytiga is abiraterone acetate 1,000 mg orally once daily with prednisone 5 mg orally twice daily, taken on an empty stomach, until disease progression occurs. 1
Dosing and Administration Details
- Dose: 1,000 mg abiraterone acetate orally once daily
- Concurrent medication: Prednisone 5 mg orally twice daily
- Administration timing: Must be taken on an empty stomach with water at least 1 hour before or 2 hours after a meal
- Administration method: Tablets should not be crushed or chewed
- Duration: Continue until disease progression is documented
- Concurrent therapy: Patients should also receive a gonadotropin-releasing hormone (GnRH) analog or should have had bilateral orchiectomy 1
Dose Modifications
- Moderate hepatic impairment (Child-Pugh Class B): Reduce starting dose to 250 mg once daily
- Hepatotoxicity during treatment: Hold abiraterone until recovery, then may reinitiate at reduced dose
- Severe hepatotoxicity: Discontinue abiraterone permanently 1
Efficacy Data Supporting This Regimen
Abiraterone acetate plus prednisone has demonstrated significant clinical benefits in mCRPC:
- Overall survival benefit: In chemotherapy-naïve patients, median OS was 35.3 months with abiraterone vs 30.1 months with prednisone alone (HR: 0.79; p=0.0151) 2
- Radiographic progression-free survival: Median rPFS was 16.5 months with abiraterone vs 8.3 months with prednisone alone (HR: 0.53; p<0.001) 3
- Secondary endpoints: Significant delays in time to pain progression, PSA progression, and need for chemotherapy 4
Monitoring Requirements
- Blood pressure: Monitor at least monthly
- Serum potassium: Monitor at least monthly
- Liver function tests: Regular monitoring required
- Signs of fluid retention: Monitor at least monthly 1
Common Adverse Effects to Monitor
- Mineralocorticoid excess: Hypertension, hypokalemia, fluid retention/edema
- Hepatotoxicity: Elevated liver enzymes
- Other common effects: Fatigue, arthralgia, hot flushes, diarrhea, nausea, vomiting 1
Important Cautions
- Cardiac events: Though rare, increased risk of atrial fibrillation and other cardiac events
- Drug interactions: Avoid strong CYP3A4 inducers; use caution with CYP2D6 substrates
- Hypoglycemia: Monitor blood glucose in patients with diabetes 1
Special Considerations
- The micronized fine-particle formulation of abiraterone is not recommended for use in mCRPC as it has different pharmacokinetics and is not interchangeable with the standard formulation 4
- Low-dose abiraterone (250 mg) with food has been studied in small trials but is not currently recommended as standard practice 4
This treatment regimen has demonstrated meaningful improvements in survival and quality of life with a generally manageable safety profile in patients with mCRPC, making it an important therapeutic option for these patients.