Evaluation of ²²³Ra therapy on bone metastases of prostate cancer by ¹⁸F-fluoride PET/CT, ¹⁸F-FDG PET/CT and bone scintigraphy/SPECT

Purpose: The aim of this study was to evaluate ²²³Ra therapy on prostate cancer with bone metastases by ¹⁸F-fluoride PET/CT, ¹⁸F-FDG PET/CT, bone scintigraphy/SPECT, and follow-up.

Methods: Ten patients with bone metastases of prostate cancer were retrospectively enrolled. As the treatment with ²²³Ra, 55kBq/kg ²²³Ra was intravenously injected. ²²³Ra treatment was performed every 4 weeks 6 times. Before the start of ²²³Ra treatment and after 6th treatment, the patients were assessed by ¹⁸F-fluoride PET/CT, ¹⁸F-FDG PET/CT, bone scintigraphy/SPECT. ¹⁸F-fluoride PET/CT and ¹⁸F-FDG PET/CT were performed 60 minutes after intravenous administration of 2.1MBq/kg of ¹⁸F fluoride or 3.7MBq/kg of ¹⁸F-FDG using a PET/CT camera (Biograph 16 or Biograph Horizon, Siemens). Bone scintigraphy/SPECT was performed 3 hours after intravenous administration of 740MBq of ^99mTc-MDP or ^99mTc-HMDP using gamma camera (Symbia T, Siemens). ROIs were drawn on the areas of bone metastases, and the maximal standardized uptake value (SUVmax) within ROIs was measured. PSA levels were compared before and after ²²³Ra therapy.

Results: Improvement of bone metastases and decrease in SUVmax confirmed after ²²³Ra therapy in 8 patients. Deterioration of bone metastases was observed in 2 patients. Bone metastases were more efficiently detected by ¹⁸F-fluoride PET/CT than bone scintigraphy/SPECT. The activity of bone metastases was more efficiently detected by ¹⁸F-FDG PET/CT than others. PSA levels were increased in 7 patients after ²²³Ra therapy.

Conclusions: The reducing effect of ²²³Ra on bone metastases was confirmed by ¹⁸F-fluoride PET/CT, ¹⁸F-FDG PET/CT, and bone scintigraphy/SPECT in 8 of the 10 patients with bone metastases of prostate cancer, although PSA levels were elevated in 7 of the patients after ²²³Ra therapy.