Effects of furosemide and tracer selection on urinary activity and peri-bladder artefacts in PSMA PET/CT: a single-centre retrospective study

BACKGROUND: High urinary activity in urinary bladder and ureters may hamper interpretation of prostate cancer and regional nodal metastases in prostate-specific membrane antigen (PSMA) PET/CT. The goal of this study was to assess effects of furosemide and choice of tracer on urinary activity in the bladder and ureters, as well as on occurrence of peri-bladder artefacts in PET/CT. METHODS: Four cohorts with a total of 202 men staged with PSMA PET/CT for prostate cancer received either (68)Ga-PSMA-11 as tracer, with (cohort G+) or without 10mg intravenous furosemide (G−) concurrent with tracer, or (18)F-DCFPyL with (F+) or without furosemide (F−). SUVmax of bladder and ureters, presence, type, and severity of peri-bladder artefacts were compared between cohorts. The influence of furosemide and choice of tracer was determined while taking differences in biodistribution time into account. RESULTS: Median SUVmax bladder was 43,5; 14,8; 61,7 and 22,8 in cohorts G−, G+, F− and F+, respectively, resulting in significant overall (p < 0.001) and between cohort differences (p adjusted < 0.001 to 0.003) except between G− and F+. Median SUVmax ureter was 6.4; 4.5; 8.1 and 6.0 in cohorts G−, G+, F− and F+, respectively, resulting in significant overall (p < 0.001) and between cohort differences for G+ : F− and F− : F+ (p < 0.001, respectively, 0.019). Significant effects of furosemide and choice of tracer on SUVmax bladder (p < 0.001 resp. p = 0.001) and of furosemide on SUVmax ureter (p < 0.001) were found, whereas differences in biodistribution time had not impacted these results significantly. Peri-bladder artefacts were present in 42/202 (21%) patients and were significantly more frequent in the F− cohort, respectively, less frequent in the G+ cohort (p = 0.001 resp. p < 0.001). Peri-bladder artefacts had a direct positive correlation with SUVmax bladder (p = 0.033). CONCLUSIONS: Increased urinary activity and higher incidence of peri-bladder artefacts were found in (18)F-DCFPyL compared to (68)Ga-PSMA-11 PET/CT. Effective reduction of urinary activity may be reached through forced diuresis using 10mg intravenous furosemide, which is especially advantageous in (18)F-DCFPyL PET/CT.