Frusemide aids diagnostic interpretation of ⁶⁸ Ga-PSMA positron emission tomography/CT in men with prostate cancer

Introduction: ⁶⁸ Ga-PSMA positron emission tomography-computed tomography (PET/CT) is useful for both staging and assessment of biochemical relapse in men with prostate cancer. Renal excretion of ⁶⁸ Ga-PSMA can lead to difficulties in scan interpretation, particularly in the pelvis. We evaluated if intravenous Frusemide at the time of ⁶⁸ Ga-PSMA injection reduces excreted activity artefact and improves diagnostic certainty.

Methods: Sixty-two men with prostate cancer undergoing clinically indicated ⁶⁸ Ga-PSMA PET/CT were prospectively included, 30 men receiving Frusemide at the time of radiotracer injection. Clinical information and reasons for the scan were documented. Intensity of excreted activity was assessed semi quantitatively for each patient (SUV max). PET/CT images were interpreted by two experienced readers for image quality, and presence/absence of PSMA-positive disease.

Results: Twenty-nine percent (18/62) were staging scans, and 71% (44/62) re-staging. PSMA-positive findings were identified in 95% (59/62). Staging scans had PSMA-positive findings within the prostate in 100% (18/18) and re-staging scans, 50% (22/44) in the prostate fossa, 64% (28/44) in lymph nodes and 21% (9/44) in viscera and bone. Administration of Frusemide had a significant impact on intensity of excreted activity in the ureters and bladder. Impaired image quality was noted in 33% (10/30) of men not given Frusemide, compared to only 3% (1/32) in men given Frusemide (P = 0.002). Reporter confidence on the presence/absence of PSMA avid disease in the prostate fossa improved from 63% (19/30) without Frusemide, to 91% (29/32) with Frusemide (P < 0.015).

Conclusion: Intravenous Frusemide given with ⁶⁸ Ga-PSMA reduces excretion artefact, and improves diagnostic certainty. Frusemide should be considered for all ⁶⁸ Ga-PSMA PET/CT imaging protocols.