Repeatability of tumor blood flow quantification with ⁸²Rubidium PET/CT in prostate cancer - a test-retest study

Non-invasive tumor blood flow (TBF) quantification is a candidate approach for risk stratification and monitoring of prostate cancer patients. Validation data have recently been published on prostate TBF measurement with the widely used positron emission tomography (PET) flow tracer ⁸²Rubidium (⁸²Rb). However, no test-retest data is available for TBF measurement with ⁸²Rb PET in prostate cancer. Such information is important to determine the potential clinical usefulness of the technique. The aim of the present study was to determine the test-retest repeatability of TBF measurement with both dynamic and static ⁸²Rb PET.

We recruited 10 low-to-high-risk prostate cancer patients scheduled for clinical prostate-specific membrane antigen (PSMA) PET/computed tomography (CT) or magnetic resonance imaging. Pelvic and cardiac static and dynamic ⁸²Rb PET/CT were performed at baseline and repeated on a different day within 1 week. In total, 11 primary lesions were analyzed.

For K1, standardized uptake values (SUV)max, SUVmean, and SUVpeak, prostate cancer ⁸²Rb PET TBF has a repeatability of 32%, 51%, 53%, and 58% and an intraclass correlation of 0.98, 0.89, 0.88, and 0.88, respectively.

Dynamic ⁸²Rb PET/CT with kinetic modeling measures TBF in prostate cancer with high repeatability, which allows identification of blood flow changes of 32%. Static late-uptake ⁸²Rb PET/CT is inferior, and only intra-individual blood flow changes above 51% can hence be recognized.