Effect of External Cooling on Lu-PSMA Uptake by the Parotid Glands.

Recent years have seen the start of treatment of metastatic castration-resistant prostate cancer with prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (PRLT), especially Lu-PSMA-617. However, PRLT has side effects on the salivary glands that limit the safety of the treatment. The current study aimed to show the effect of external cooling with ice packs on Lu-PSMA-617 uptake by the parotid glands (PGs). The study included 19 patients (mean age, 72.9 y) with metastatic castration-resistant prostate cancer who had been referred for the first time for Lu-PSMA-617 treatment and underwent pretreatment Ga-PSMA-11 PET/CT. Before the initiation of PRLT, the SUV and SUV of the right and left PGs were measured on Ga-PSMA PET/CT. Frozen ice packs were then affixed over the right PG of each patient for approximately 5 h; 1 h after they were affixed, PRLT was administered. At 4 h after PRLT, head-and-neck SPECT/CT was performed, and at both 4 and 24 h after PRLT, whole-body planar scintigraphy was performed. Regions and volumes of interest were applied for the right and left PGs, and the counts and volumes were determined. Before PRLT, Ga-PSMA-11 PET/CT showed no significant difference in SUV or SUV between the right and left PGs ( > 0.05). At 4 and 24 h after PRLT, planar imaging showed no significant difference in counts between the cooled and noncooled PGs ( > 0.05). Furthermore, at 4 h after PRLT, SPECT/CT showed no significant difference in counts or volumes between the cooled and noncooled PGs ( > 0.05). External cooling does not reduce uptake of Lu-PSMA-617 by the PGs.