Abstract
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Objectives: Non-invasive quantification of tumor blood flow (TBF) is a potential method for risk-stratification and monitoring in prostate cancer. We have recently validated 82Rubidium (82Rb) positron emission tomography (PET) for TBF measurement in prostate cancer. However, no test-retest data exist on prostate TBF measurement with 82Rb PET. This information is crucial to determine the potential clinical impact of this method. The aim of this study was to determine the reproducibility of 82Rb PET for TBF measurement.
Methods: Ten low-risk to high-risk prostate cancer patients were recruited in connection with clinical prostate specific membrane antigen (PSMA) PET/ computed tomography (CT) or magnetic resonance imaging (MRI). Static 82Rb PET/CT scans were performed of the pelvic region and retest scans were performed on a different day, within one week of the baseline scan. Since the variance of the differences depend on the mean, the analyses were performed on log-transformed data to avoid this bias.
Results: TBF with 82Rb PET can be measured in prostate tumors with an intraclass correlation of (0.89; 0.88 and 0,88); a within-subject coefficient of variance of (18.3 %; 18.9 % and 21.0 %); and a repeatability coefficient of (50.8 %; 52.3 % and 58.3 %) for SUVmax, SUVmean and SUVpeak respectively.
Conclusions: TBF measured using static 82Rb PET/CT in prostate cancer can be reproduced with a coefficient of variance and repeatability of approximately 20% and 55%, respectively, depending on SUV measure. Consequently, the method can be applied to monitor relative changes in TBF above 55% in serial exams. Financial support This work was financially supported by The Danish Cancer Society, Health Research Fund of Central Denmark Region, P. Carl Petersens Fond, Dansk Kræftforskningsfond and Knud og Edith Eriksens Mindefond.