68Ga-PSMA PET/CT imaging predicting intraprostatic tumor extent prior to radical prostatectomy in patients with prostate cancer.

Abstract

e632 Background: The performance of gallium Ga 68 (68Ga)-labeled prostate-specific membrane antigen (PSMA) ligand positron emission tomography/computed tomography (PET/CT) shows promising results with regard to lymph node detection even at low prostate specific antigen (PSA) levels in patients with biochemical recurrence after curative therapy for prostate cancer. In this study we evaluate the usefulness of PSMA-PET/CT for the evaluation of intraprostatic tumor extent prior to radical prostatectomy. Methods: In total 15 patients with prostate cancer underwent a 68Ga-PSMA-PET/CT before surgical treatment. All patients received either open or laparoscopic radical prostatectomy. Intraprostatic tumor extent was assessed on PET/CT. The peak standardized uptake value (SUV) was correlated with final whole gland histopathology including Gleason grade, lobe infiltration, TNM stage and seminal vesicle invasion. Results: Mean SUV over all patients was 10.64 ±9.19. Median Gleason score was 7. The distribution of TNM stage 2a, 2b, 2c, 3a, 3b, 4 was 0, 2, 6, 5, 2 and 0 patients. Mean intraprostatic SUV for patients with organ confined vs. extraprostatic tumor on histopathology was 6.3 and 15 respectively (p = 0.043). Mean SUV for patients with a Gleason score of ≤ 7a and > 7a was 6.2 and 13.5 (p = 0.046). Sensitivity and specificity for identifying tumor invasion of a prostate lobe was 84.6% and 75% (Positive and negative predictive value (PPV, NPV) for prostate lobe invasion were 95.7% and 42.9%). Sensitivity and specificity for seminal vesicle invasion were 50% and 100% (PPV 100%, NPV 96.6%). Conclusions: These early results need to be further validated in a larger cohort.