What is the recommended treatment for prostate cancer that has metastasized to the ribs?

Treatment of Prostate Cancer Metastatic to the Ribs

For prostate cancer metastatic to the ribs, initiate androgen deprivation therapy (ADT) with an LHRH agonist or bilateral orchiectomy as first-line systemic treatment, and offer external beam radiotherapy (single 8 Gy fraction or 10 fractions of 3 Gy) for painful rib metastases. 1

Systemic Treatment Approach

First-Line Hormonal Therapy

• Androgen suppression using bilateral orchiectomy or an LHRH agonist is the cornerstone first-line treatment for metastatic prostate cancer. 1
• When initiating LHRH agonists, administer a short-course antiandrogen to prevent disease flare from the initial testosterone surge. 1
• Continue androgen suppression even if the disease progresses to castration-refractory status. 1

Chemotherapy for Symptomatic Disease

• Docetaxel 75 mg/m² every 3 weeks combined with prednisone 5 mg orally twice daily should be considered for symptomatic, castration-refractory metastatic prostate cancer. 1, 2
• Docetaxel is FDA-approved specifically for metastatic castration-resistant prostate cancer in combination with prednisone. 2

Radiation Therapy for Rib Metastases

External Beam Radiotherapy Options

• For painful rib metastases, a single fraction of 8 Gy is equally effective as 10 fractions of 3 Gy for pain relief and is more cost-effective. 1, 3
• Both fractionation schemes provide equivalent pain-reducing efficacy in castration-refractory disease. 1
• Single-fraction treatment (8 Gy) is particularly appropriate for non-vertebral metastases like ribs. 3

Radiopharmaceuticals for Widespread Disease

• Radioisotope therapy with strontium-89 or samarium-153-EDTMP should be considered for patients with painful bone metastases from castration-refractory disease. 1
• Radium-223 is indicated for patients with symptomatic bone metastases and no known visceral disease, as it significantly improves overall survival (median 14.9 vs 11.3 months). 3
• Radium-223 emits high-energy alpha particles with shorter path length, reducing toxicity to adjacent tissue compared to beta-emitters. 3
• Radium-223 is well-tolerated with low rates of grade 3/4 hematologic toxicity (3% neutropenia, 6% thrombocytopenia, 13% anemia). 3

Additional Supportive Measures

Bisphosphonates for Refractory Pain

• Intravenous bisphosphonates (e.g., pamidronate) should be considered for patients with bone pain resistant to palliative radiotherapy and conventional analgesics. 1

Palliative Care Integration

• Patients with castration-refractory disease should be managed in collaboration with dedicated palliative care services. 1

Treatment Algorithm

1. Immediate systemic control: Start LHRH agonist (with short-course antiandrogen) or perform bilateral orchiectomy 1
2. Pain management: If rib metastases are painful, offer single 8 Gy fraction external beam radiotherapy 1, 3
3. Disease progression: If castration-refractory develops, continue ADT and add docetaxel for symptomatic disease 1, 2
4. Widespread bone pain: Consider radium-223 if multiple symptomatic bone metastases without visceral disease 3
5. Refractory pain: Add intravenous bisphosphonates if pain persists despite radiotherapy 1

Important Caveats

• Do not use docetaxel in patients with neutrophil counts <1500 cells/mm³ or abnormal liver function (bilirubin >ULN). 2
• The safety of chemotherapy after radium-223 has not been established; preliminary data suggest avoiding combination with standard-dose docetaxel. 3
• Retreatment with a second course of external beam radiation can induce pain responses in approximately 50% of patients if initial treatment fails. 4