Results of a randomized Phase-3 trial to evaluate the efficacy of strontium-89 adjuvant to local field external beam irradiation in the management of endocrine resistant metastatic prostate cancer

A large proportion of the practice of radiotherapy in the management of metastatic adenocarcinoma of the prostate is associated with palliation of pain from osseous metastases and improving quality of life. Strontium-89 is a systemic radionuclide that has clinical efficacy in the palliation of pain from bony metastases. The study was a Phase-3 randomized placebo control trial performed in eight Canadian Cancer Centers to evaluate the effectiveness of strontium-89 as an adjunct to local field radiotherapy. Patients with endocrine refractory metastatic prostate cancer received local field radiotherapy and either strontium-89 as a single injection of 10.8 mCi or placebo. One hundred twenty-six patients were recruited. No significant differences in survival or in relief of pain at the index site were noted. Intake of analgesics over time demonstrated a significant reduction in the arm treated with strontium-89. Progression of pain as measured by sites of new pain or the requirement for radiotherapy showed statistically significant differences between the arms in favor of strontium-89. Tumor markers including prostate specific antigen, acid phosphatase, and alkaline phosphatase were also reduced in patients receiving strontium-89. A Quality-of-Life analysis was performed as a multivariate data set and demonstrated an overall superiority of strontium-89 with alleviation of pain and improvement in physical activity being statistically significant. Toxicity was evaluated and demonstrated increased hematological toxicity in the group receiving strontium-89. It is concluded that the addition of strontium-89 is an effective adjuvant therapy to local field radiotherapy reducing progression of disease as evidenced by new sites of pain and the requirement of further radiotherapy and improving quality-of-life and need for analgesic support in this group of patients. 24 refs., 7 figs., 2 tabs