What type of radiation therapy is recommended for metastatic prostate cancer?

Radiation Therapy for Metastatic Prostate Cancer

For metastatic prostate cancer, external beam radiotherapy (EBRT) should be offered for painful bone metastases using either a single 8 Gy fraction or 30 Gy in 10 fractions, and radiopharmaceutical therapy with agents like radium-223 should be considered for patients with widespread symptomatic bone metastases without visceral disease. 1, 2

External Beam Radiotherapy for Bone Metastases

• A short course of 800 cGy (8 Gy) in a single fraction is as effective and less costly than 3000 cGy (30 Gy) in 10 fractions for non-vertebral metastases 2, 1
• Both fractionation schedules (1×8 Gy or 10×3 Gy) provide equal pain-relieving efficacy for painful bone metastases from castration-refractory disease 2, 1
• EBRT is particularly important for patients with localized bone pain and can provide significant symptom relief 2

Radiopharmaceutical Therapy

• Radiopharmaceuticals are indicated for patients with widespread metastatic disease, particularly when they are no longer candidates for effective chemotherapy 2, 1
• Radium-223 is FDA-approved specifically for patients with castration-resistant prostate cancer with symptomatic bone metastases and no known visceral metastatic disease 3
• Radium-223 has been shown to improve overall survival (median 14.9 vs 11.3 months compared to placebo) and prolong time to first skeletal-related event (median 15.6 vs 9.8 months) 1
• Other radiopharmaceuticals commonly used include strontium-89 (89Sr) and samarium-153 (153Sm) 2, 1

Treatment Algorithm for Metastatic Prostate Cancer

1. First-line therapy: Androgen suppression using bilateral orchiectomy or an LHRH agonist/antagonist 2, 4

   • Short-course antiandrogen should be used to prevent disease flare when starting an LHRH agonist 2, 4

2. For painful bone metastases:

   • External beam radiotherapy with either single 8 Gy fraction or 30 Gy in 10 fractions 2, 1
   • For patients with widespread bone metastases: Consider radiopharmaceuticals (radium-223, strontium-89, or samarium-153) 2, 1

3. For castration-refractory disease:

   • Continue androgen suppression 2
   • Consider second-line hormonal therapy (antiandrogens, corticosteroids) 2
   • For symptomatic disease: Consider docetaxel using a 3-weekly schedule 2
   • For bone pain resistant to radiotherapy and conventional analgesics: Consider intravenous bisphosphonates 2, 1

Important Considerations and Pitfalls

• Radium-223 is generally well-tolerated with relatively low rates of grade 3/4 hematologic toxicity (3% neutropenia, 6% thrombocytopenia, 13% anemia) 1
• The safety of using chemotherapy after radium-223 has not been established, and preliminary data suggest combination with standard doses of docetaxel should be avoided 1
• Patients with metastatic disease should be managed in collaboration with dedicated palliative care services to optimize symptom management 2, 1
• Recent evidence suggests that EBRT to the primary tumor may improve survival in selected metastatic prostate cancer patients with low PSA levels and intermediate life expectancy (5-10 years) 5

Monitoring and Follow-up

• Regular assessment of pain response after palliative radiotherapy is essential to determine the need for additional interventions 1
• Continued monitoring of PSA levels and imaging studies to evaluate disease progression and treatment response 2
• Careful monitoring for side effects of both radiotherapy and concurrent androgen deprivation therapy 4