An 70-year-old man with castration-resistant metastatic prostate cancer has symptomatic osteoblastic bone metastases on bone scan but no visceral metastases. He receives six injections of a radiopharmaceutical that homes to areas of increased bone turnover and relieves pain while improving survival. This agent is:
- A Strontium-89 chloride
- B Samarium-153 lexidronam
- C Radium-223 dichloride ✓
- D Technetium-99m MDP
Correct answer: C. Radium-223 dichloride
Explanation
Radium-223 dichloride is an alpha-emitting calcium mimetic that incorporates into newly formed bone matrix at osteoblastic metastatic sites. It is the only bone-seeking radiopharmaceutical shown to improve overall survival in metastatic castration-resistant prostate cancer with symptomatic bone-only disease. Strontium-89 and samarium-153 are beta emitters providing palliation without survival benefit, and Tc-99m MDP is purely diagnostic.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.