A comparative study of samarium-153-ethylenediaminetetramethylene phosphonic acid with pamidronate disodium in the treatment of patients with painful metastatic bone cancer.

OBJECTIVE To assess the therapeutic efficacy and toxicity of samarium-153-ethylenediaminetetramethylene phosphonic acid ((153)Sm-EDTMP) and pamidronate disodium in patients with painful metastatic bone cancer. SUBJECTS AND METHODS Eighteen patients with histopathologically confirmed malignancy and multifocal bone metastases were randomized into two equal groups of 9 patients each. Group A was treated with (153)Sm-EDTMP, while group B was treated with pamidronate disodium. The pain score for each patient was recorded before and after therapy using visual analogue scales that graded both the intensity and frequency of the bone pain. Therapeutic response was classified as inefficient, mild, effective and excellent. RESULTS Pain score in each group prior to therapy was more than 6. In group A, 2 (22.2%) and 7 (77.8%) cases showed mild and effective response, respectively. The therapeutic efficacy of (153)Sm-EDTMP was adjudged to be 77.8%. Transient myelosuppression was generally mild and reversible with white blood cells and platelets recovering after 6 weeks. In group B, palliative response in 4 cases (44.4%) was inefficient, in 1 case (11.1%) mild, in 3 cases (33.3%) effective and in 1 case (11.1%) excellent, with a therapeutic efficacy of 44.4% for pamidronate disodium. No hematological toxicity was noted. CONCLUSION The data showed that the therapeutic efficacy of (153)Sm-EDTPM was higher than that of pamidronate disodium (for pain relief maintained more than 3 weeks) and its incidence of blood toxicity was also higher than that of pamidronate disodium.