Strontium-89 chloride

Strontium-89 chloride (branded Metastron) is indicated for the relief of bone pain in patients with painful skeletal metastases, confirmed by a prior bone scan; it is not a treatment for the underlying cancer and does not relieve pain from soft tissue disease. The FDA label recommends a fixed dose of 148 MBq (4 mCi) by slow intravenous injection over one to two minutes, or a weight-based alternative of 1.5-2.2 MBq/kg (40-60 microCi/kg); repeat dosing is generally not recommended at intervals of less than 90 days and depends on haematological recovery.

Strontium-89 decays by beta emission with a physical half-life of 50.5 days; roughly two-thirds of excretion is urinary and one-third faecal in patients with bone metastases, with retention in metastatic lesions lasting much longer than the roughly 14-day turnover in normal bone. Pain relief typically begins 10-20 days after injection and can last three to six months; a transient pain flare in the first few days is common.

Metastron was originally marketed by Amersham/Zeneca and later GE Healthcare; the branded product was discontinued and the compound is now supplied generically (marketed as Strontium89). It sits alongside samarium-153 lexidronam and radium-223 dichloride as FDA/EMA-approved bone-palliation radiopharmaceuticals, though 89Sr and 153Sm are not tumour-type-restricted the way radium-223's label is limited to castration-resistant prostate cancer.