Targeted "bone-seeking" radiopharmaceuticals for palliative treatment of bone metastases: A systematic review and meta-analysis

Aim. The aim of the study was to assess the state of the art of the use of bone-seeking radiopharmaceuticals for palliation therapy of pain from bone metastases. Methods. A systematic literature search was conducted about therapy with ⁸⁹Sr-chloride and ¹⁵³Sm-EDTMP between 2001-2011. The primary outcomes were efficacy and toxicity. Descriptive and quantitative data were extracted from each study, calculating event rates and odds ratio (OR) with 95% confidence intervals (CI) for pooled analysis. Subgroup analyses were performed. Results. Fifty-seven studies contributed to the systematic review. Forty-six studies used radiopharmaceuticals as a single agent, 15 investigated therapeutic combinations. Most of the studies included patients with prostate cancer. The overall efficacy of bone-seeking radiopharmaceuticals as single agents was 70%, whereas it was 74% when used in combination with other therapies. Complete response was reported in 27% of patients. Efficacy resulted to be 70% for prostate cancer and 79% for breast cancer. The overall toxicity of radiopharmaceuticals was 15%: the toxicity was 11% selecting only studies reporting on the use of radiopharmaceuticals as a single agent. No significant difference was found between bone-seeking radiopharmaceuticals and other oncological treatments regarding efficacy or toxicity. Reports of objective response outcomes suggest that bone-seeking radiopharmaceuticals have some cytotoxic activity, either alone or combination with chemotherapy. Conclusion. This literature analysis emphasizes multiple evidences of high efficacy and low toxicity of bone seeking radiopharmaceuticals; moreover, this therapy may have a therapeutic potential beyond simple palliation of bone pain.