Dose estimation in strontium-89 radiotherapy of metastatic prostatic carcinoma

Strontium-89 radiotherapy is becoming an important treatment in the palliation of bone pain from osteoblastic metastases. The absorbed dose delivered to bone metastases during 89Sr radiotherapy has been estimated in four patients with metastatic prostatic carcinoma. Patients were injected with a tracer dose of 85Sr-chloride. Blood and urine samples were obtained during the week following injection. Strontium-85 scintigrams of metastases and normal bone were obtained up to 8 wk postinjection. Half of the patients showed elevated whole-body retention; plasma-strontium concentrations were decreased from normal values. Uptake of strontium in metastases was 2-25 times that in normal bone but rates of washout of strontium from metastases were similar to those from normal bone. Absorbed doses delivered in infinite time to the metastases by 89Sr ranged from 21 +/- 4 to 231 +/- 56 cGy/MBq with a median value of 68 cGy/MBq. Doses to red marrow were less by a factor of 2 to 50. These absorbed doses are sufficiently large to be expected to produce a therapeutic benefit.