Role of 68Ga-PSMA PET/CT in Initial Staging of Prostate Cancer and Correlation with PSA and Gleason Score

Abstract

Background Prostate cancer is the second most common male malignancy. Its prognosis depends on the tumor stage as well as its aggressiveness; expressed histopathologically by Gleason scores. Furthermore, optimal patient management depends on the tumor stage. 68Ga PSMA PET/CT has a wide spectrum of uses in prostate malignancy, some of them are comprehensively studied while others are still under investigation. The most widely accepted use is the accurate initial staging of cancer prostate as well as predicting the long-term outcome, with SUVmax being a promising prognostic parameter correlating significantly with other established prognostic parameters, including the Gleason score and the PSA levels. Objective To evaluate the role of 68GA- PSMA PET/CT in initial staging of prostate cancer and correlate with PSA level and Gleason score. Methods A prospective descriptive study over the course of 6 months. It included patients with pathologically proven prostate cancer referred for a PSMA PET/CT scan for initial staging without any treatment or interventions. Results 68Ga-PSMA PET/CT scans of 36 patients were evaluated for local staging (primary prostatic lesions, extra-prostatic spread, and seminal vesicle invasion), regional nodal staging, and metastatic spread (extra-regional lymph nodes, osseous lesions, and visceral lesions). PET/CT findings as well as the SUVmax of the most avid lesions were correlated with PSA level, Gleason scores, as well as Gleason grade risk groups. A statistically significant relationship was found between PSA level and SUVmax of prostatic lesion as well as that of the most avid metastatic regional lymph node, the presence of extra-regional lymph nodal spread, the presence of osseous metastatic lesions, the presence of seminal vesicle invasion, extra-prostatic extension, and the presence of PSMA-avid regional lymph nodal spread. On the other hand, a statistically significant relationship was found between Gleason scores and the presence of regional lymph nodal spread and osseous metastatic lesions. Lastly, a statistically significant relationship was found between Gleason grading risk groups and the presence of regional lymph nodal spread and osseous metastatic lesions. Conclusion 68Ga-PSMA PET/CT is a powerful staging and stratifying tool for the majority of prostate cancer patients, being significantly correlated with PSA level and Gleason scores. However, patients with low PSA scores still pose a dilemma as they showed significantly low PSMA uptake, rendering the use of 68Ga-PSMA PET/CT for staging in such patients controversial. 68Ga-PSMA PET/CT based imaging findings should ideally be supported with histopathological documentation and/or follow-up imaging results in order to confirm the nature of detected lesions and help establish accurate sensitivity and specificity of 68Ga-PSMA PET/CT.