Bone-seeking radionuclides for therapy

Systemic therapy using bone-seeking radiopharmaceuticals has clear advantages for the treatment of multisite metastatic pain. Evidence supporting the use of beta-particle, electron, and alpha-particle-emitting radiopharmaceuticals is reviewed here. Appropriate patient selection relies on correlating clinical symptoms with focal abnormalities on conventional bone scintigraphy. Time to symptom relief and response duration vary with the physical half-life and dose rate of the radionuclide used, offering the opportunity to tailor radiopharmaceutical choice to individual patient circumstances. Toxicity is limited to temporary myelosuppression, governed by the administered activity and underlying bone marrow reserve. Optimal responses are achieved in patients with a modest skeletal tumor burden, suggesting that targeted therapy should be considered early in the management of bone metastases. The development of reliable dosimetric models will facilitate patient-specific prescribing to deliver enhanced symptom response within acceptable toxicity limits. It is likely that targeted therapy will be most effective in the context of multimodality tumor management. Further research is required to examine the potential of radionuclides in combination with external-beam irradiation, bisphosphonates, or chemotherapy. This approach might allow targeted therapy to progress beyond symptom palliation to early intervention for survival gain.