Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography Compared with Conventional Imaging for Initial Staging of Treatment-naïve Intermediate- and High-risk Prostate Cancer: A Retrospective Single-center Study

Background: The role of prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) imaging in the initial staging of men with prostate cancer (PCa) has yet to be evaluated adequately.

Objective: To investigate the concordance of PSMA PET/CT with conventional imaging (CI) with cross-sectional abdominopelvic and/or radionuclide bone imaging in the initial staging of patients with treatment-naïve PCa.

Design, setting, and participants: We performed a post hoc retrospective cohort study of patients enrolled in a prospective single-arm trial (NCT03368547). We included patients with intermediate-risk (IR) and high-risk (HR) PCa who underwent PSMA PET/CT within 6 mo of CI. Patients with any treatment prior to PSMA PET/CT were excluded. Patient- and tumor-specific data, and imaging findings were obtained.

Outcome measurements and statistical analysis: Our primary outcome measurement was the concordance rate of PSMA PET/CT with CI for the identification of N, M1a, M1b, and M1c disease. Descriptive statistics were used.

Results and limitations: A total of 168 patients with treatment-naïve IR and HR PCa met the inclusion criteria. HR disease accounted for 124/168 (73.8%) patients. The median prostate-specific antigen was 11.4 (6.8-24.6)ng/ml. The rates of nonconcordance between PSMA PET/CT and CI were 34/162 (21.0%), 5/70 (7.1%), 8/92 (8.7%), and 1/71 (1.4%) for N, M1a, M1b, and M1c disease, respectively. PSMA PET/CT assigned a higher stage in 37/168 (22.0%) patients and a lower stage in 12/170 (7.1%) patients. In a subset of 50 patients treated with radical prostatectomy and pelvic lymph node dissection, the prevalence of PSMA PET/CT-positive and that of CI-positive nodal disease were 14% and 4%, and the false negative rates were 30% and 32%, respectively. The principal limitations of this study include the heterogeneity in CI modalities and the 6-mo time frame between CI and PSMA PET.

Conclusions: PSMA PET/CT imaging may serve as a valuable tool in the initial staging of treatment-naïve IR and HR PCa.

Patient summary: We evaluated how prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) compared with standard imaging (such as computed tomography, bone scan, and prostate magnetic resonance imaging) for initial staging of patients with prostate cancer. Our findings suggest that PSMA PET/CT may detect and rule out more metastatic lesions, which could prove valuable in guiding treatment.