Tumour blood flow for prediction of human prostate cancer aggressiveness. A study with Rubidium-82 PET, MRI and Na${}^{+}$/K${}^{+}$-ATPase-density

Tumour blood flow (TBF) is a crucial determinant of cancer growth. Recently, we validated Rubidium-82 (${}^{82}$Rb) positron emission tomography (PET) for TBF measurement in prostate cancer (PCa) and found TBF and cancer aggressiveness positively correlated. The aims of the present study were to determine the ability of TBF for separating significant from insignificant PCa and to examine the relation to underlying Na${}^{+}$/K${}^{+}$-ATPase density, which is relevant as ${}^{82}$Rb is transported intracellularly via the Na${}^{+}$/K${}^{+}$-ATPase. One hundred and two patients were included for pelvic ${}^{82}$Rb PET scan prior to magnetic resonance imaging (MRI)-guided prostate biopsy. Findings constituted 100 PCa lesions (86 patients) and 25 benign lesions (16 patients). Tumours were defined on MRI and transferred to ${}^{82}$Rb PET for TBF measurement. Immunohistochemical Na${}^{+}$/K${}^{+}$-ATPase staining was subsequently performed on biopsies. TBF was the superior predictor (rho = 0.68, p < 0.0001, inflammatory lesions excluded) of MRI-guided biopsy grade group (GG) over lowest apparent diffusion coefficient (ADC) value (rho = −0.23, p = 0.01), independent of ADC value and tumour volume (p < 0.0001). PET could separate GG-2-5 from GG-1 and benign lesions with an area under the curve (AUC), sensitivity, and specificity of 0.79, 96%, and 59%, respectively. For separating GG-3-5 from GG-1-2 and benign lesions the AUC, sensitivity, and specificity were 0.82, 95%, and 63%, respectively. Na${}^{+}$/K${}^{+}$-ATPase density per PCa cell profile was 38% lower compared with that of the benign prostate cell profiles. Neither cell density nor Na${}^{+}$/K${}^{+}$-ATPase density determined tumour ${}^{82}$Rb uptake. TBF is an independent predictor of PCa aggressiveness and deserves more attention, as it may be valuable in separating clinically significant from insignificant PCa.