Evaluation of treatment efficacy of metastatic bone pain with 153Sm-EDTMP

Introduction: Involvement of the skeleton can cause excruciating pain in two-third of terminal patients with the history of malignancy. According to several limitations of other therapies, such as analgesics, bisphosphonates, chemotherapy, hormonal therapy and external beam radiotherapy, bone-seeking radiopharmaceuticals have an important role in palliation of pain from bone metastases. Although these kind of therapies have many advantages including the ability to treat multiple sites of tumoral involvement simultaneously, no significant confliction with other treatments, ease of administration and the potential to be used repetitively; in Iran using of this modality is not widely practiced. In this study we evaluated the clinical usefulness of Sm-153 lexidronate for pain management of bone metastases. Methods: 14 patients with the history of painful bone metastases caused by different cancers (5 prostate, 5 breast, 1 lung and 4 nasopharynx), not responding to conventional treatments were included in the study. All patients had recent whole body bone scan indicating multiple bone metastases. 1 mCi/Kg Sm-153 lexidronate was injected intravenously to the patients. Whole body Sm scintigraphy was done 3 and 18 hours post injection. Pain relief and quality of life have been evaluated by analog pain scale and Karnofsky index every week respectively. Also all patients were evaluated for hematological toxicity every two weeks. Active follow up was performed. Results: 64% of patients showed presence of flare phenomen between 24 to 72 hours after Sm injection with mean duration of 3.7 days. Three patients (21%) showed complete relief of pain and 9 (64%) achieved partial response to therapy. (Over all response to therapy was 85%). Karnofsky index significantly increased in 57% of study patients. 71% and 50% of patients showed decreased in platelets and leukocytes respectively after two weeks which was backed to primary range between 4 to 8 weeks post injection. No one experienced hematological toxicity induced problem. No significant difference has been noted between 3 and 18 hours post injection images quality. Conclusion: Sm-153 lexidronate is an effective treatment for painful bone metastases. The complication rate is low and the quality of life of the patients after treatment would be significantly improved.