What is the appropriate management and monitoring for a patient with prostate cancer on Abiraterone (TIGA) 1000 mg daily and prednisone 5 mg daily?

Management and Monitoring for Prostate Cancer Patients on Abiraterone (TIGA) and Prednisone

Abiraterone (TIGA) 1000 mg daily with prednisone 5 mg daily must be continued until disease progression, with monthly monitoring of blood pressure, potassium, liver function, phosphate levels, and signs of fluid retention to prevent serious complications. 1

Dosing and Administration

• Standard dosing:

  • Abiraterone 1000 mg (four 250 mg tablets) once daily on an empty stomach
  • Prednisone 5 mg once daily with food (breakfast)
  • Alternative lower-cost option: 250 mg daily with a low-fat breakfast 1

• Administration requirements:

  • Take abiraterone on an empty stomach (1 hour before or 2 hours after meals)
  • Food significantly impacts absorption, leading to unpredictable effects
  • Prednisone must be continued while on abiraterone to prevent mineralocorticoid excess 1, 2

Required Monitoring Schedule

Monthly Monitoring (Essential)

• Blood pressure (22% develop hypertension, 4% severe) 1, 2
• Potassium levels (17-28% develop hypokalemia) 2
• Liver function tests (AST/ALT) (11-12% develop liver injury) 1, 2
• Phosphate levels (24% develop hypophosphatemia) 2
• Signs of fluid retention/peripheral edema (28% develop edema) 2

Every 2-3 Months

• Complete blood count (WBC may decrease)
• PSA levels to assess treatment response 1

Every 4 Months

• Comprehensive metabolic panel including bilirubin 1

Side Effect Management

Cardiovascular Monitoring

• Monitor for:
  • Peripheral edema (28% of patients)
  • Atrial fibrillation (4% of patients)
  • Congestive heart failure
  • Increased heart rate
  • Patients with pre-existing cardiovascular disease need particularly careful monitoring 1, 2

Metabolic Effects

• Monitor for:
  • Hyperglycemia (consider metformin if needed)
  • Elevated ACTH levels
  • Dizziness (common side effect)
  • Mental fog (common side effect)

Other Common Side Effects

• Fatigue (39% of patients)
• Back or joint discomfort (28-32%)
• Hot flushes (22%)
• Urinary frequency and nocturia
• Dyspepsia
• Upper respiratory tract infection 2

Important Precautions

Handling Precautions

• Wash hands after handling abiraterone
• Apply hazard precautions (not chemotherapy but requires careful handling)

Prednisone Management

• Critical point: Prednisone must NOT be stopped abruptly while on abiraterone
• If abiraterone is discontinued, prednisone should be tapered gradually
• Prednisone is essential to prevent mineralocorticoid excess from abiraterone 1

Mechanism of Action and Rationale

Abiraterone works by blocking testosterone synthesis through inhibition of the CYP17 enzyme:

• Blocks testosterone production throughout the body
• Reduces androgen-driven prostate cancer growth
• Part of androgen deprivation therapy (ADT)
• Affects adrenal pathway, requiring prednisone supplementation 1

Special Considerations

1. Switching formulations: Do not switch between different formulations of abiraterone upon disease progression 1

2. Alternative approach for disease progression: Consider switching from prednisone to dexamethasone 1 mg/day if disease progression occurs on abiraterone with prednisone 1

3. Food effects: If using the lower-cost option (250 mg with low-fat breakfast), monitor closely for side effects and return to standard dosing if excess toxicity occurs 1

4. Maintain castrate testosterone levels: Continue androgen deprivation therapy throughout treatment 2

By following this comprehensive monitoring protocol, you can effectively manage patients on abiraterone therapy while minimizing complications and optimizing treatment outcomes.