A Prospective Study on [Ga]-PSMA PET/CT Imaging in Newly Diagnosed Intermediate- and High-Risk Prostate Cancer.

Objectives: Prostate-specific membrane antigen (PSMA) ligand positron emission tomography/computed tomography (PET/CT) is an emerging modality to detect metastatic disease in patients with prostate cancer (PCa). This prospective study aimed to evaluate the role of [Ga]-PSMA PET/CT in the initial workup of intermediate and high-risk PCa.

Methods: Twenty-five patients with newly transrectal ultrasound biopsy-proven, untreated intermediate- and high-risk PCa (mean age, 68.5±6.2 years; range 55-83 years) were enrolled in this prospective study between September 2018 and June 2020 and underwent a [Ga]-PSMA PET/CT examination. All images were analyzed both visually and semiquantitatively by measuring the maximum standardized uptake value (SUV) of the primary prostatic tumor and metastatic lesions. The diagnostic sensitivity of [Ga]-PSMA PET/CT for the diagnosis of PCa was established by histopathology as the reference standard. The associations between SUV of the primary tumors and prostate-specific antigen (PSA) levels, Gleason scores (GSs), and metastatic extent of the disease were studied.

Results: All patients had a positive [Ga]-PSMA PET/CT exam. Seventeen patients (58%) showed [Ga]-PSMA avidity in both prostate lobes and 8 (32%) had unilateral uptake. SUV in the primary tumor significantly correlated with serum PSA values (r=0.57, P=0.003). PSMA PET/CT depicted regional lymph node metastases in 32% of patients, distant lymph node metastases in 20%, osseous metastases in 16% and pulmonary metastases in 8% of patients. Sixty percent of PSMA-positive bone metastases and 21.4% of intraprostatic tumoral lesions were missed on the contemporaneous bone scintigraphy and magnetic resonance imaging, respectively.

Conclusion: [Ga]-PSMA PET/CT shows promise as a valuable imaging modality with high diagnostic sensitivity in the setting of intermediate and high-risk PCa. Moreover, the SUV of the primary tumor has a positive correlation with PSA levels at the time of the scan.