Assessment of Prostate Carcinoma Aggressiveness: Relation to<sup>68</sup>Ga-PSMA-11-PET/MRI and Gleason Score
Jiří Ferda, Ondřej Hes, Milan Hora, Eva Ferdová, Jan Pernický, Vladimir Rudnev, Ladislav Pecen, Ondřej Topolčan, Hynek Mírka
Abstract
Background/Aim: To test the correlation of <sup>68</sup>Ga-PSMA-11 uptake and the expression of PSMA (prostatic specific membrane antigen) with the Gleason score, apparent diffusion coefficient (ADC) and pharmacokinetic parameters obtained from dynamic contrast agent-enhanced MRI/PET. Patients and Methods: Forty newly diagnosed, therapy naïve patients with prostatic carcinoma (PC) (mean age of 56.7, range=34-79), who were referred for <sup>68</sup>Ga-PSMA-11-PET/MRI for primary staging and had undergone radical prostatectomy (RAPE) were included in this prospective study. Their blood samples were tested for serum levels of prostate-specific antigen (PSA) and proPSA. The patients’ prostates were evaluated using whole-mount sections, which helped determine the extent and grade of the tumor; tests were performed to determine immunohistochemical PSMA expression. Results: A correlation between PSMA expression and the accumulation of <sup>68</sup>Ga-PSMA-11 was found using the Spearman correlation coefficient (p=0.0011). A stronger correlation was found between Gleason patterns 3 or 4 and PSMA expression (p=0.06). Furthermore, the correlation of Gleason score with the overall <sup>68</sup>Ga-PSMA-11 accumulation within the tumor or non-tumor tissue was found to be significant (p=0.0157). A significant relation was found only with the K<sub>ep</sub> elimination rate constant, which was stronger in Gleason pattern 4 than in Gleason pattern 3. A weaker correlation was found between the accumulation of <sup>68</sup>Ga-PSMA-11 and K<sup>trans</sup> in Gleason pattern 4: the most significant relation being between ADC<sub>min</sub> and Gleason pattern 3 and 4 (p=0.0074). The total size of the tumor correlated with levels of proPSA (p<0.0001), and its extra prostatic extension correlated with levels of proPSA (p<0.0001). Conclusion: <sup>68</sup>Ga-PSMA-11 correlates well with the expression of PSMA. Gleason pattern 3 and 4 had a higher correlation with <sup>68</sup>Ga-PSMA-11 levels than did Gleason pattern 5. Either no correlation, or a weak correlation, was established with pharmacokinetics.