Predictors of Response to Strontium-89 (Metastron®) in Skeletal Metastases from Prostate Cancer: Report of a Single Centre's 10-Year Experience

Abstract An analysis of prospectively collected data from 75 patients with bone metastases secondary to prostate cancer who were treated with strontium-89 injection in a single centre over a 10-year period, is presented. The surrogate role of markers of disease progression (haemoglobin and prostate specific (PSA) antigen levels; number of bone scan-positive sites), symptomatic factors (analgesic intake; number of painful bone sites) and history of prior external radiotherapy, were analysed to determine whether any parameters had a predictive effect on the success of strontium-89 treatment. The success of strontium-89 injection was determined by calculating the change in number of sites of bone pain (pain sites) and analgesic intake. The outcome was classed as successful in 42 (56.0%) patients, unsuccessful in 13 (17.3%) and unchanged in 20 (26.7%). Proportionately more of the patients who had ‘superscans' on bone scintigraphy at baseline had an unsuccessful outcome after a strontium-89 injection (5/7; 71.4%); for those with fewer bone scan-positive sites the majority had successful outcomes. Patients with a successful outcome had a significantly better survival rate after strontium- 89 injection. Multivariate analysis showed haemoglobin level, PSA level and outcome after strontium-89 treatment to be significant independent prognostic variables; no change/unsuccessful outcome, a high PSA level prior to treatment, and a low haemoglobin level were associated with poor survival. It is suggested that early treatment with strontium-89 (Metastron®) in patients with fewer bone metastases is more likely to be successful, with a longer time before further therapy required.