Systemic administration of new therapeutic radioisotopes, including phosphorus, strontium, samarium, and rhenium.
New advances in systemic radionuclide therapy have increased the number of treatment options available for patients with painful osseous metastases. This form of therapy has three major appeals: 1) it addresses all sites of involvement; 2) selective absorption into bone limits irradiation of normal tissues; and 3) as a result, toxicity may be reduced and the therapeutic ratio improved. The clinical experience with radioactive phosphorus, strontium, samarium, and rhenium are reviewed. To date, the best studied and the only Food and Drug Administration approved agent is strontium-89. About 60% to 90% of patients treated with strontium-89 respond with complete or partial relief of pain for a median duration of 6 months. Large, prospectively randomized clinical trials have established the efficacy of strontium-89 as a first-line therapy and as an adjuvant to external-beam radiotherapy. Particularly advantageous is its usefulness in situations in which external-beam radiotherapy options have been exhausted and normal tissue tolerance has been reached. Newer radiopharmaceuticals are still under investigation.