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

(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.

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.

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).

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.

Journal of medical imaging and radiation oncology. 2017 Jun 17 [Epub ahead of print]

Niall Fennessy, Jonathan Lee, Jane Shin, Bao Ho, Syed Aman Ali, Royce Paschkewitz, Louise Emmett

Department of Nuclear Medicine, St Vincent's Public Hospital, Sydney, Australia., University of New South Wales, Sydney, New South Wales, Australia.