ESMO Asia Congress 2022

Abstract 172P

Background

68-Ga PSMA PET/CT has become a new reference standard for prostate cancer (Pca) imaging beyond conventional techniques. This study aims to compare the role of 68-Ga PSMA PET/CT and conventional imaging for staging and re-staging in nonmetastatic Pca who have biochemical Recurrence and evaluate the impacts on management.

Methods

Retrospective analysis of 64 nonmetastatic Pca patients who had biological failure with serum PSA rising in Ramathibodi Hospital from Jan 2017-Dec 2021. We compared the diagnostic accuracies of Ga-68 PSMA PET/CT and conventional imaging modalities to assess primary disease, lymph node involvement, and distant metastasis. The patient characteristics, Gleason score, serum PSA cut-off by Youdens’ index, patient-based sensitivity, specificity, positive (PPV), and negative predictive values (NPV) were assessed.

Results

Median patient age was 68 years (range 50-83). 46.88% of patients changed staging to metastatic stage post evaluation with 68-Ga PSMA/PET and 22.22% defined as oligo-metastasis. The efficacy in identifying either pelvic nodal or distant-metastatic disease that 68Ga-PSMA PET/CT showed a patient-based sensitivity, specificity, PPV, and NPV compared with conventional imaging were 68%, 89.5%, 94.4%, and 51.5%, respectively. Following 68Ga PSMA PET/CT, 25% of patients had changes in cancer management. Serum PSA cut-off for diagnosed biochemical recurrence post radical treatment using 68Ga PSMA PET/CT scan was below 1.03 ng/ml demonstrating the ROC was 0.71, sensitivity 52.20% (95% CI 39.80-64.40%), and specificity 90.00% (95% CI 79.50-96.20%).

Conclusions

68Ga PSMA PET/CT scans show higher sensitivity, specificity, PPV, and NPV beyond conventional imaging. 68Ga PSMA PET/CT significantly impacted changing management for non-metastatic biochemical recurrence prostate cancer patients.