A multiinstitutional, concurrent chemoradiation trial of strontium-89, estramustine, and vinblastine for hormone refractory prostate carcinoma involving bone.

Abstract

Estramustine phosphate (EMP) and vinblastine have radiosensitizing properties and significant activity against hormone refractory prostate carcinoma. Strontium-89 is a palliative agent that acts as a selective radiation source for bone metastasis. The combination of EMP, vinblastine, and strontium-89 was developed to exploit the potential for radiosynergy. PATIENTS AND METHODS Forty-four patients at the Brown Oncology Group affiliated hospitals were treated with oral EMP 600 mg/m2 daily on Weeks 1-4 and 7-10, vinblastine 4 mg/m2 intravenously once each week on Weeks 1-4 and 7-10, and strontium-89 2.2 MBq/kg on Day 1. Courses were repeated every 12 weeks. Response assessment was based on a change in the serum prostate specific antigen (PSA) levels, correlated with change in measurable disease and bone scan appearance. A greater than or equal to 50% decline in PSA for at least 6 weeks was observed in 21 patients (48%, 95% confidence interval, 33-62%). Median duration of response was 23 weeks (range, 6-70.8 weeks). The median survival was 13 months with 1- and 2-year survival rates of 55% and 25%, respectively. After completion of protocol therapy, a retrospective review showed that only nine patients received subsequent palliative external beam radiation after progression. The addition of strontium-89 to the regimen of EMP and vinblastine can be delivered safely and in repeated doses, provides effective palliation, and may decrease the need for future radiation therapy. A randomized trial is necessary to quantify these effects.