Introduction:

To maximize quality of life in prostate cancer patients undergoing radical prostatectomy (RP) surgery, knowing the presence and location of extraprostatic extension (EPE) is required to utilize a less aggressive nerve-sparing (NS) approach. Magnetic resonance imaging (MRI) has improved detection of EPE, but limitations exist. New advancements in PET imaging with prostate specific membrane antigen (PSMA) have shown promising results. To explore a more accurate EPE prediction method, we sought to retrospectively analyze clinical and PSMA-PET CT features that predict EPE.

Methods:

A retrospective review of clinical, PSMA-PET CT imaging, and histopathology data was conducted among patients who underwent a ⁶⁸Ga-PSMA-PET CT scan followed by RP and whole-mount pathologic analysis between September 2017 and May 2022. We calculated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for PSMA-PET in predicting EPE. We then generated a receiver operating characteristic (ROC) curve and calculated the area under the curve (AUC) for numerous clinic-radiologic parameters. PSMA-PET and clinical variables associated with EPE and their respective thresholds were identified: lesion diameter >= 1.5cm, curvilinear contact length >5mm, and Gleason grade group >2.

Results:

We identified 109 patients that underwent PSMA-PET prior to surgical intervention with histopathology data for comparison. The mean age at RP was 62 ± 6 (standard deviation); total individual PSMA-PET segment (right and left) count was 218 and 63/218 (29%) of segments had pathologic EPE. With PSMA-PET alone, Sensitivity was 0.78, Specificity was 0.79, PPV was 0.61, and NPV was 0.90. ROC curves were generated and with PSMA-PET alone, the AUC was 0.81; when adding a Gleason grade group threshold (>2), the AUC was 0.82. For a curvilinear contact length >5mm, 49/81 (61%) had pathologic EPE; when adding diameter and Gleason grade group thresholds, 29/40 (73%) had pathologic EPE.

Conclusion:

PSMA-PET CT curvilinear contact length of >5mm was identified as the strongest predictor of pathologic EPE while PET diameter >1.5cm and Gleason grade group >2 were also predictive.

Funding: N/A