⁶⁸Ga-prostate-specific membrane antigen-theranostics and ²²³Ra in prostate cancer: an Innsbruck experience

Progression to androgen independence is the first cause of mortality in metastasized castration resistant prostate cancer (CRPC) patients. For this reason, a targeted theranostic approach based on increased expression of prostate-specific membrane antigen (PSMA) on PC cells is an attractive and quickly developing treatment option. At the Medical University of Innsbruck, the condition of all CRPC patients was discussed in the institutional tumor board. Patients with extensive skeletal metastases usually receive ²²³Ra treatment (Xofigo^®, 6 X 50 kBq/kg monthly), and patients who show skeletal and soft tissue metastases and who show progressive disease under a combination therapy of ²²³Ra and enzalutamide are scheduled for experimental ¹⁷⁷Lu-PSMA617 therapy. We conclude that CRPC patients should be treated earlier during the course of the disease, and patients with lymph node and visceral metastases should receive ¹⁷⁷Lu-PSMA617 treatment. Our data suggest that the ⁶⁸Ga/¹⁷⁷Lu-PSMA-targeted theranostic concept could evolve into an important treatment option for metastasized CRPC. We conclude that ¹⁷⁷Lu-PSMA617-ligand therapy in patients with CRPC is clinically safe and can be effective in patients with progressive CRPC. A larger prospective study is needed to address the multitude of questions arising with this new treatment modality, especially to timing, dosing, and response evaluation. Furthermore, the potential of combined ¹⁷⁷Lu-PSMA617 with ²²³Ra therapy and/ or radiosensitizing chemotherapeutic drugs should be further explored