Whole-Body 177Lu–Prostate-Specific Membrane Antigen Scan Pattern With Excess Free 177Lu-Chloride in a Metastatic Castration-Resistant Prostate Cancer Patient

Abstract

A 56-year-old man with metastatic castration-resistant prostate cancer was referred for radioligand therapy with 177Lu–prostate-specific membrane antigen. In the third cycle, a posttherapy whole-body scan showed unexpected skeletal and joint uptake apart from his known metastatic lesions. This observation raised suspicion for possible impurity (mainly free lutetium) in the applied radiopharmaceutical product. After contacting the radiopharmaceutical company, we were informed that the radiochemical purity of the used batch of 177Lu–prostate-specific membrane antigen had been 95%. This is the first report of excess free lutetium scan pattern and its complications in a patient undergoing radioligand therapy.