Effect of External Cooling on ¹⁷⁷Lu-PSMA Uptake by the Parotid Glands.

Abstract

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 ¹⁷⁷Lu-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 ¹⁷⁷Lu-PSMA-617 uptake by the parotid glands (PGs). <b>Methods:</b> 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 ¹⁷⁷Lu-PSMA-617 treatment and underwent pretreatment ⁶⁸Ga-PSMA-11 PET/CT. Before the initiation of PRLT, the SUV_max and SUV_mean of the right and left PGs were measured on ⁶⁸Ga-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. <b>Results:</b> Before PRLT, ⁶⁸Ga-PSMA-11 PET/CT showed no significant difference in SUV_max or SUV_mean between the right and left PGs (<i>P</i> > 0.05). At 4 and 24 h after PRLT, planar imaging showed no significant difference in counts between the cooled and noncooled PGs (<i>P</i> > 0.05). Furthermore, at 4 h after PRLT, SPECT/CT showed no significant difference in counts or volumes between the cooled and noncooled PGs (<i>P</i> > 0.05). <b>Conclusion:</b> External cooling does not reduce uptake of ¹⁷⁷Lu-PSMA-617 by the PGs.