Because there is great interest in systemic therapies for metastatic prostate cancer, I want to provide readers with the latest news about the Lu-177-PSMA-617 trials in Germany.
I recently reported (see this link) on 74 patients – 31% had PSA declines greater than 50%. A new report by Rahbar et al. expands the patient base to include PSA data on 99 patients and toxicity data on 121 patients treated at 12 therapy centers. After median follow-up of 16 weeks, and up to 4 therapy cycles:
· 45% had a PSA decline greater than 50%
o 40% after a single cycle
· 18/121 patients (15%) had serious or life-threatening hematotoxicity, affecting red blood cells (10%), platelets (4%), and white blood cells (3%)
· Xerostomia (loss of saliva) occurred in 8%
This is a very encouraging PSA response. For comparison, only 13% had a PSA reduction greater than 50% in the Xofigo clinical trial. However in that trial, 66% had a 50%+ decline in bone alkaline phosphatase, which may be a better biomarker for bone metastases. The hematotoxicity was identical.
What we really want to know is whether the treatment increases survival, and whether it is any better than Xofigo in doing so. The potential benefit of Lu-177-PSMA-617 is that it can treat non-osseous metastases too. We await future clinical trials to prove its benefit.