Presentation Authors: Michael Frumer, Jack Baniel, Petach Tikva, Israel, Serge Bistritsky, Gilad E. Amiel, Azik Hoffman, Haifa, Israel, Nadav Milk, Itay Sternberg, Ilan Leibovitch, Kfar Saba, Israel, Itay Sagy, Kfar Saba and Haifa, Israel, Gal Rinott Mizrahi, Yoram Dekel, Haifa , Israel, Amnon Zisman, Miki Haifler, Rishon LeZion, Israel, Shay Golan*, Petach Tikva, Israel
Introduction: There is considerable variance in the reported accuracy of Ga68-PSMA PET/CT (PSMA PET/CT) and multiparametric MRI (mpMRI) for regional staging of prostate cancer (PCa). We estimated the negative predictive value of these modalities in patients who underwent radical prostatectomy.
Methods: A multicenter cohort of patients who underwent PET/CT and MRI prior to radical prostatectomy was analyzed. All patients underwent standard pelvic lymph node dissection. Increased Ga68-PSMA uptake on PET/CT and enlarged (>10 mm) lymph nodes (LN) on MRI were considered positive findings. The final surgical pathology served as standard of reference. The negative predictive value (NPV) was calculated for each modality separately as well as the combined. Due to inherent selection bias, the positive predictive value was not calculated.
Results: 58 patients with intermediate or high risk PCa were included. The median PSA level was 8.5 ng/ml (IQR: 5.7-14.2). Pre-operative grade group was 4 or 5 in 26 patients (44%), 3 in 14 patients (24%), 2 in 17 patients (30%) and 1 in one patient (2%). . The median number of extracted LN was 11 (IQR: 6-18). Metastatic LN involvement was found in 11 patients (19%). A single positive node was found in 7/11 patients (64%). The median maximal diameter of the involved LN and the median intra nodal tumor diameter were 6 mm (IQR: 3.5- 10) and 1 mm (IQR: 1- 3) mm, respectively. The Negative predictive value of PET/CT, MRI, and the two tests combined were 82.3%, 81.8%, and 83.6%, respectively.
Conclusions: Ga68-PSMA PET/CT and multiparametric MRI demonstrated similar performance in excluding pelvic lymph nodes metastases with NPV of approximately 82%. Combination of both tests did not improve the negative predictive value significantly. Our results reinforce the need for pelvic lymph nodes dissection in order to achieve accurate staging.