Samarium-153 treatment of bone pain in patients with metastatic prostate cancer.

Introduction: Painful bone metastases are common in advanced prostate cancer. We report the clinical outcome after administration of Samarium-153 ((153)Sm), an emitter of beta-particles that concentrates in the areas of enhanced osteoblastic activity.
Methods: Twenty-two patients (median age 73 years) with metastatic, hormone-refractory prostate cancer received a single bolus infusion of (153)Sm (37 MBq/kg). All patients had painful bone metastases to more than one anatomical region, and most had inadequate pain relief to narcotic analgesics. Bone specific pain, analgesic score according to WHO, ECOG performance status, and blood count were evaluated before and up to 28 weeks after treatment.
Results: Median follow-up was six weeks (mean 14 weeks). Eleven patients died within the 28 week observation period (ten from terminal disease), and four patients had their observation period truncated. Median pain score was 56.3%, 50.0%, and 50.0% of baseline values at week 4 (n = 20), 16 (n = 10), and 28 (n = 7), respectively. A reduction of baseline pain score by 50% or more was observed in 50%, 70% and 71% of patients at week 4, 16, and 28, respectively. Hematological toxicity was mild and reversible in most cases.
Conclusion: Administration of (153)Sm to prostate cancer patients with painful bone metastases offered clinical relevant pain relief with tolerable hematological toxicity.