Palliation of pain associated with metastatic bone cancer using samarium-153 lexidronam: A double-blind placebo-controlled clinical trial

Purpose: To evaluate the effectiveness and safety of samarium-153 (¹⁵³Sm) lexidronam (EDTMP) in a double-blind, placebo-controlled study. Portents and Methods: Patients with painful bone metastases secondary to a variety of primary malignancies were randomized to receive ¹⁵³Sm-EDTMP 0.5 or 1.0 mCi/kg, or placebo. Treatment was unblinded for patients who did not respond by week 4, with those who had received placebo eligible to receive 1.0 mCi/kg of active drug in an open-label manner. Patient and physician evaluations were used to assess pain relief, as was concurrent change in opioid analgesia. Results: One hundred eighteen patients were enrolled onto the study. Patients who received 1.0 mCi/kg of active drug had significant reductions in pain during each of the first 4 weeks in both patient-rated and physician-rated evaluations. Pain relief was observed in 62% to 72% of those who received the 1.0-mCi/kg dose during the first 4 weeks, with marked or complete relief noted in 31% by week 4. Persistence of pain relief was seen through week 16 in 43% of patients who received 1.0 mCi/kg, of active drug. A significant correlation (P = .01) was observed between reductions in opioid analgesic use and pain scores only for those patients who received 1.0 mCi/kg ¹⁵³Sm-EDTMP. Bone marrow suppression was mild, reversible, and not associated with grade 4 toxicity. Conclusion: A single dose of 1.0 mCi/kg of ¹⁵³Sm-EDTMP provided relief from pain associated with bone metastases. Pain relief was observed within 1 week of administration and persisted until at least week 16 in the majority of patients who responded.