Characterizing and Mitigating Bladder Radioactivity on ¹⁸F-Fluciclovine PET/CT

Area of Science:

• Nuclear Medicine
• Radiopharmaceutical Imaging
• Oncology

Background:

• 18F-fluciclovine PET is utilized for prostate cancer recurrence detection.
• Clinical observations suggest higher-than-expected bladder excretion of 18F-fluciclovine.
• Radiopharmaceutical package insert indicates minimal urinary excretion within the first 4 hours.

Purpose of the Study:

• To quantify early bladder radioactivity after 18F-fluciclovine administration.
• To assess the impact of voiding protocols on bladder radioactivity.
• To determine if withholding voiding before injection mitigates bladder activity.

Main Methods:

• 159 patients undergoing 18F-fluciclovine PET/CT were divided into two groups: voiding before injection (n=36) and not voiding before injection (n=123).
• Standardized Uptake Values (SUVmax, SUVmean) for bladder, aorta, marrow, and liver were measured.
• Bladder radioactivity was categorized based on SUVmean relative to background organs.

Main Results:

• Overall, 22% of patients exhibited moderate and 8.8% intense bladder activity.
• A negative association was observed between bladder volume and SUVmean.
• The non-voiding group showed significantly lower rates of moderate (17.1% vs 38.9%) and intense (4.9% vs 22.2%) bladder activity compared to the voiding group.

Conclusions:

• Withholding voiding prior to 18F-fluciclovine injection effectively reduces urinary bladder radioactivity.
• This modified protocol is recommended to prevent potential masking or mimicry of prostate cancer recurrence.
• Further investigation into the mechanisms of 18F-fluciclovine bladder accumulation is warranted.