The influence of forced diuresis on detection rate in ⁶⁸ Ga-PSMA-11 PET/CT in recurrent PC: an intra-patient analysis

Ziel/Aim The urinary excretion of PSMA-ligands with resultant high bladder activity can obscure locally relapsing prostate cancer (PC) lesions in Positron-Emission-Tomography/Computed Tomography (PET/CT). While a number of studies report the role of forced diuresis in PSMA-PET/CT, its influence on local recurrence detectability has not been extensively studied, which this present study aims to address.

Methodik/Methods 76 patients underwent biphasic [⁶⁸Ga]Ga-PSMA-11 PET/CT at 1.5h and 2.5h for detecting recurrent PC and were retrospectively analysed. 20 mg of Furosemide i.v. was administered at 1h p.i. with 1L of oral hydration. Additional ‘late’ imaging at 2.5h p.i. was without additional diuretics or standardised hydration.

Comparing the post-diuresis and late imaging afforded an intrapatient model for the influence of bladder activity. First, blinded consensus read was undertaken by two nuclear medicine physicians. An unblinded read was then performed, and examples of discrepancy were noted. SUV_max values for PC lesions, SUV_mean for the bladder and background activity were noted.

Clinical follow up was performed for correlative data.

Ergebnisse/Results Post-diuretic imaging revealed 44 locally recurrent lesions, whereas late scans showed 40 locally recurrent lesions (p=0.06). The n=4 lesions were located in 4/76 patients (5.3 %). At late imaging (without additional furosemide and hydration), the bladder activity was significantly higher compared to standard imaging thereby obscuring n=4 lesions. Follow up showed a clear change in clinical management for at least one of these patients.

Schlussfolgerungen/Conclusions Post diuresis imaging and hydration increased local lesion detectability, which did not continue into late imaging. While the role for diuresis in PSMA imaging is well established, its implementation is far from universal, and the optimal imaging protocol is yet to be established, for which further prospective studies are required.