Retrospective analysis of [99mTc]Tc-HYNIC-PSMA single photon emission computed tomography CT in patients with prostate cancer.

Objective: Prostate cancer is one of the most common malignancies in men. While multiparametric MRI is the gold standard for local staging of prostate cancer, accessibility may be limited. The same is true for Prostate Specific Membrane Antigen (PSMA) PET/computed tomography (CT). This study evaluates the diagnostic performance of [99mTc]Tc-PSMA single photon emission computed tomography (SPECT) as an alternative molecular imaging modality.

Methods: This retrospective study of 82 patients with newly diagnosed prostate cancer compares the performance of [99mTc]Tc-PSMA SPECT/CT with multiple readers, with MRI, and with respect to histopathological correlation from biopsies. SPECT/CT findings were evaluated both locally, using a standardised 12-segment prostate model, and with respect to metastases. Agreement between modalities and readers was measured using intraclass correlation and Cohen's kappa.

Results: PSMA SPECT/CT identified clinically relevant prostate lesions with the best interreader agreement for bone metastases and laterality, and poorest agreement for extraprostatic extension and seminal vesicle invasion. Sector-based comparison showed PSMA SPECT/CT to have comparable detection rates to MRI. Higher SPECT standardised uptake values (SUV) were associated with stronger concordance with biopsy results, higher than both the low SPECT SUV group and clinical MRI readings.

Conclusion: [99mTc]Tc-PSMA SPECT/CT demonstrates promise as an alternative to MRI in the primary staging of prostate cancer, particularly in high SPECT SUV settings. While MRI remains more sensitive for local extension, PSMA SPECT may offer complementary value in comprehensive staging, especially in a resource-limited setting.