Head-to-Head Comparison of 18F-PSMA-1007 Positron Emission Tomography/Computed Tomography and Multiparametric Magnetic Resonance Imaging with Whole-mount Histopathology as Reference in Localisation and Staging of Primary Prostate Cancer

Abstract

Background: Accurate local staging is critical for treatment planning and prognosis in prostate cancer (PCa). Although multiparametric magnetic resonance imaging (mpMRI) has high specificity for detection of extraprostatic extension (EPE) and seminal vesicle invasion (SVI), its sensitivity remains limited. ¹⁸F-PSMA-1007 positron emission tomography/computed tomography (PET/CT) may be more accurate in determining T stage.

Objective: To assess the diagnostic performance of ¹⁸F-PSMA-1007 PET/CT in comparison to mpMRI for intraprostatic tumour localisation and detection of EPE and SVI in men with primary PCa undergoing robot-assisted radical prostatectomy (RARP).

Design, setting, and participants: Between February 2019 and October 2020, 105 treatment-naïve patients with biopsy-proven intermediate- or high-risk PCa undergoing mpMRI and ¹⁸F-PSMA-1007 PET/CT before RARP were prospectively enrolled.

Outcome measurements and statistical analysis: The diagnostic accuracy of ¹⁸F-PSMA-1007 PET/CT and mpMRI for intraprostatic tumour localisation and detection of EPE and SVI was assessed via histopathological examination of whole-mount RP specimens. The sensitivity, specificity, negative predictive value, positive predictive value, and accuracy were calculated. The McNemar test was used to compare outcomes between imaging modalities.

Results and limitations: In 80 RP specimens, 129 PCa lesions were found, of which 96 were clinically significant PCa (csPCa). Per-lesion sensitivity for localisation of overall PCa was 85% (95% confidence interval [CI] 77-90%) with PSMA PET/CT and 62% (95% CI 53-70%) with mpMRI (p < 0.001). Per-lesion sensitivity for csPCa was 95% (95% CI 88-98%) with PSMA PET/CT and 73% (95% CI 63-81%) with mpMRI (p < 0.001). The diagnostic accuracy of PSMA PET/CT and mpMRI for detection of EPE per lesion did not significantly differ (sensitivity 45%, 95% CI 31-60% vs 55%, 95% CI 40-69%; p = 0.3; specificity 85%, 95% CI 75-92% vs 90%, 95% CI 81-86%; p = 0.5). The sensitivity and specificity of PSMA PET/CT and mpMRI for detection of SVI did not significantly differ (sensitivity 47%, 95% CI 21-73% vs 33%, 95% CI 12-62; p = 0.6; specificity 94%, 95% CI 88-98% vs 96%, 95% CI 90-99%; p = 0.8).

Conclusions: ¹⁸F-PSMA-1007 is a promising imaging modality for localising intraprostatic csPCa but did not show additional value in assessing EPE and SVI in comparison to mpMRI.

Patient summary: A new imaging technique called PET/CT (positron emission tomography/computed tomography) with the radioactive tracer ¹⁸F-PSMA-1007 shows promise in identifying the location of clinically significant prostate cancer. However, it does not seem to be of additional value over magnetic resonance imaging (MRI) for determining the local tumour stage.

Keywords: (18)F-PSMA-1007 positron emission tomography/computed tomography; Diagnostic accuracy; Local staging; Multiparametric magnetic resonance imaging; Prostate cancer; Tumour localisation.