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High activity rhenium-186 hydroxyethylidene diphosphonate (HEDP) with autologous peripheral blood stem cell (PBSC) transplant: A novel treatment strategy in hormone refractory prostate cancer metastatic to bone.

4562 Background: Bone marrow is the dose-limiting organ for bone seeking radionuclide therapy of bone metastases from prostate cancer. This prospective phase 2 trial investigated the potential for improvement in disease control by using autologous peripheral blood stem cell transplant to permit administration of high activities of a bone seeking radionuclide, Rhenium-186 HEDP in patients with progressive hormone refractory prostate cancer.


METHODS
Eligible patients had histologically confirmed prostate cancer metastatic to the skeleton, rising PSA despite castrate testosterone levels, WHO PS 0-1, and minimal soft-tissue disease. Patients received between 4500 and 5000MBq of Rhenium-186 HEDP i.v. (approximately 4 times the dose normally used for palliation), followed 14 days later by the return of pre-harvested PBSCs. Response was assessed using PSA, survival, pain scores, and quality of life measurement.


RESULTS
Thirty-eight patients with a median age of 67 years (range 50-77), and a median PSA of 57 ng/ml (range 4-3628) received a median activity of 4978 MBq Rhenium-186 HEDP (range 4400-5097). At a median follow up of 12 months (range 3-32), the most serious toxicity was short-lived (<7 days) grade 3 thrombocytopenia in 8 (21%) patients. The median survival of the group is 31 months with a Kaplan-Meier estimated 1 and 2-year survivals of 81% and 50% respectively. Twenty six patients (60%, 95% CI, 45-74%) had stable or reduced PSA levels 3 months post therapy, 10 of whom had PSA reductions of > 50% lasting > 4 weeks. Quality of life measures were stable or improved in 29 (76%) at 3 months.


CONCLUSIONS
We believe the survival data and PSA response rates in this group of heavily pre-treated patients are encouraging and merit further investigation in a randomised trial. No significant financial relationships to disclose.