Cancer therapy using bone-seeking isotopes.

Bone pain is a common symptom in disseminated malignancy and may be difficult to manage effectively. Radiation is of proven benefit for pain palliation and there is growing interest in the therapeutic potential of bone-seeking radiopharmaceuticals. Clinical data relating to the use of phosphorus-32, strontium-89, samarium-153 EDTMP, rhenium-186 HEDP and tin-117m DTPA are reviewed in the context of the pathophysiology of metastatic bone pain. Possible mechanisms of action of palliative radiotherapy and, in particular, the theoretical role of early response genes are discussed. The application of Monte Carlo simulation to targeted radiotherapy for bone metastases may provide the basis for a clearer understanding of the microdosimetry and radiobiology of bone pain palliation and for reliable prediction of clinical response and toxicity.