Significance of metabolic tumor volume and total lesion uptake measured using Ga-68 labelled prostate-specific membrane antigen PET/CT in primary staging of prostate cancer.

Objective: To evaluate the accuracy of Ga-68 prostate-specific membrane antigen positron-emission-tomography and computed-tomography(PSMA-PET/CT) in primary nodal staging of prostate cancer (PCa), and the predictive value of volumetric parameters derived from Ga-68- PSMA-PET/CT data in lymph node(LN) metastasis and correlation with histopathological and surgical outcomes.

Materials And Methods: Seventy-seven patients with newly diagnosed, biopsy-proven PCa who underwent Ga-68-PSMA-PET/CT for primary staging of disease and underwent radical prostatectomy with extendend pelvic LN dissection were evaluated retrospectively. 2 experienced nuclear medicine specialists have retrospectively reviewed PET/CT images blinded to all histopathological and clinical data. Sensitivity, specificity, positive predictive value(PPV), and negative predictive value(NPV) for the detection of LN metastases were analyzed per-patient. Volumetric and semiquantitative PET parameters of the primary prostate lesions including SUVmax,metabolic tumor volume(MTV), and total lesion uptake(TLU) were measured and recorded.

Results: Primary tumor SUVmax, MTV and TLU were found significantly higher in patients who were in higher ISUP Grade groups 3,4,5 after surgical treatment (P = 0.021,P = 0.049,P = 0.032, respectively). The sensitivity, specificity, PPV and NPV on LN metastasis detection of Ga-68-PSMA-PET/CT was found 60%, 91%, 82% and 78% respectively. Although the distribution of the measured primary tumor MTV and TLU values were higher in histopathologically proven LN metastasis positive patients compared to negative patients, only TLU was statistically significant(P = 0.023). Increase in primary tumor TLU values were correlated with higher pT stages and surgical margin positivity(P = 0.034).

Conclusion: Ga-68-PSMA-PET/CT is of clinically valuable for primary staging. Measuring and adding these 2 parameters in routine clinical evaluation may increase the prediction power of high-grade disease confirmed by surgery.