Strontium-89 and Low-Dose Infusion Cisplatin for Patients with Hormone Refractory Prostate Carcinoma Metastatic to Bone: A Preliminary Report

Strontium-89 has been used for the treatment of painful bony metastases in patients suffering from disseminated adenocarcinoma of the prostate, with a variable proportion of patients obtaining clinically significant reductions in analgesic requirements. Based on data revealing enhancement of continuous low-dose rate irradiation by low-dose cisplatin in murine models, a protocol using 148 MBq (4 mCi) of 89Sr and 35 mg/m2 of cisplatin infused over 2 days, 1 and 4 wk after administration of the radioisotope was undertaken. Preliminary data suggest good pain relief with 55% of 18 patients entered thus far obtaining at least a 50% reduction in analgesic requirements. Improvements in total alkaline phosphatase and serum lactate dehydrogenase have consistently been seen, with some patients exhibiting improvements in hemoglobin, tumor markers and bone scans. Toxicity appears to be mild, with no life-threatening complications. In particular, myelosuppression after one course of treatment was modest, but retreatments in two patients has resulted in grade 3 hematologic toxicity. Two patients developed a "pain flare" after administration of cisplatin. Further accrual to this study will allow more accurate determination of pain response rate, and improved evaluation of parameters of objective response.