Prostate ⁸²Rb PET tumor blood flow measurement for detection of significant prostate cancer

Objectives: Our previous studies suggest that tumor blood flow measured with ⁸²Rb Positron Emission Tomography (PET) has potential as a biomarker of prostate cancer aggressiveness (1,2). The aim of the present study was to evaluate whether ⁸²Rb PET can separate significant from insignificant prostate cancer.

Methods: 102 patients suspected of having prostate cancer were included prior to MRI-guided prostate biopsies. ⁸²Rb PET scan of the prostate gland was performed in all patients. Prostate cancer was biopsy-verified and given a Gleason Grade Group (GGG) in 98 lesions from 85 of the patients. Twenty-eight lesions were GGG1, 50 lesions were GGG2, six lesions were GGG3, nine lesions were GGG4 and five lesions were GGG5. Twenty-six lesions from 17 patients were biopsied with benign findings. Tumor delineation was performed at MR scans and subsequently fused with the ⁸²Rb PET scans for measurement of tumor uptake of ⁸²Rb.

Results: Tumor ⁸²Rb SUVmax was the best indicator of MRI-guided biopsy Gleason Grade Group with a moderate correlation (rho=0.57, p<0.0001) compared to ADC-value and tumor volume on MRI. SUVmax was a significant predictor of Gleason Grade Group, even after correction for ADC value and tumor volume (p<0.0001). Mean ⁸²Rb SUVmax uptake in low-risk prostate cancer of 2.87 with 95% CI [2.56; 3.17] was significantly lower than in both intermediate-risk 3.74 [3.53; 3.95], and high-risk prostate cancer 4.17 [3.63; 4.71] (p<0.001). With an AUC of 0.81, ⁸²Rb PET could separate GGG2-5 from GGG1 and benign biopsies with a sensitivity of 0.89 and a specificity of 0.69. And for separating GGG3-5 from GGG1-2 and benign biopsies the AUC was 0.83, with a sensitivity of 0.90 and a specificity of 0.68.

Conclusions: Tumor ⁸²Rb uptake is a significant predictor of Gleason Grade Group, independent of MRI-based ADC value and tumor volume. Hence, tumor blood flow may provide additional value in separating significant from insignificant prostate cancer. Financial support: This work was financially supported by The Danish Cancer Society, Health Research Fund of Central Denmark Region, P. Carl Petersens Mindefond, Aage og Johanne Louis-Hansens Fond, Harboefonden, Aase og Ejnar Danielsens Fond, Dagmar Marshalls Fond, Knud og Edith Eriksens Mindefond, Fabrikant Einar Willumsens Mindelegat, Agnes og Poul Friis Fond, Tømmerhandler Vilhelm Bangs Fond.