A Prospective Comparison of 18F-prostate-specific Membrane Antigen-1007 Positron Emission Tomography Computed Tomography, Whole-body 1.5 T Magnetic Resonance Imaging with Diffusion-weighted Imaging, and Single-photon Emission Computed Tomography/Computed Tomography with Traditional Imaging in Primary Distant Metastasis Staging of Prostate Cancer (PROSTAGE)

Abstract

BackgroundComputed tomography (CT) and bone scintigraphy (BS) are the imaging modalities currently used for distant metastasis staging of prostate cancer (PCa). ObjectiveTo compare standard staging modalities with newer and potentially more accurate imaging modalities. Design, setting, and participantsThis prospective, single-centre trial (NCT03537391) enrolled 80 patients with newly diagnosed high-risk PCa (International Society of Urological Pathology grade group ≥3 and/or prostate-specific antigen [PSA] ≥20 and/or cT ≥ T3; March 2018–June 2019) to undergo primary metastasis staging with two standard and three advanced imaging modalities. Outcome measurements and statistical analysisThe participants underwent the following five imaging examinations within 2 wk of enrolment and without a prespecified sequence: BS, CT, 99mTc-hydroxymethylene diphosphonate (99mTc-HMDP) single-photon emission computed tomography (SPECT)-CT, 1.5 T whole-body magnetic resonance imaging (WBMRI) using diffusion-weighted imaging, and 18F-prostate-specific membrane antigen-1007 (18F-PSMA-1007) positron emission tomography(PET)-CT. Each modality was reviewed by two independent experts blinded to the results of the prior studies, who classified lesions as benign, equivocal, or malignant. Pessimistic and optimistic analyses were performed to resolve each equivocal diagnosis. The reference standard diagnosis was defined using all available information accrued during at least 12 mo of clinical follow-up. Patients with equivocal reference standard diagnoses underwent MRI and/or CT to search for the development of anatomical correspondence. PSMA PET-avid lesions without histopathological verification were rated to be malignant only if there was a corresponding anatomical finding suspicious for malignancy at the primary or follow-up imaging. Results and limitationsSeventy-nine men underwent all imaging modalities except for one case of interrupted MRI. The median interval per patient between the first and the last imaging study was 8 d (interquartile range [IQR]: 6–9). The mean age was 70 yr (standard deviation: 7) and median PSA 12 ng/mL (IQR:7–23). The median follow-up was 435 d (IQR: 378–557). Metastatic disease was detected in 20 (25%) patients. The imaging modality 18F-PSMA-1007 PET-CT had superior sensitivity and highest inter-reader agreement. The area under the receiver-operating characteristic curve (AUC) values for bone metastasis detection with PSMA PET-CT were 0.90 (95% confidence interval [CI]: 0.85–0.95) and 0.91 (95% CI: 0.87–0.96) for readers 1 and 2, respectively, while the AUC values for BS, CT, SPECT-CT, and WBMRI were 0.71 (95% CI: 0.58–0.84) and 0.8 (95% CI: 0.67–0.92), 0.53 (95% CI: 0.39–0.67) and 0.66 (95% CI: 0.54–0.77), 0.77 (95% CI: 0.65–0.89) and 0.75 (95% CI: 0.62–0.88), and 0.85 (95% CI: 0.74–0.96) and 0.67 (95% CI: 0.54–0.80), respectively, for the other four pairs of readers. The imaging method 18F-PSMA-1007 PET-CT detected metastatic disease in 11/20 patients in whom standard imaging was negative and influenced clinical decision making in 14/79 (18%) patients. In 12/79 cases, false positive bone disease was reported only by PSMA PET-CT. Limitations included a nonrandomised study setting and few histopathologically validated suspicious lesions. ConclusionsDespite the risk of false positive bone lesions, 18F-PSMA-1007 PET-CT outperformed all other imaging methods studied for the detection of primary distant metastasis in high-risk PCa. Patient summaryIn this report, we compared the diagnostic performance of conventional and advanced imaging. It was found that 18F-prostate-specific membrane antigen-1007 positron emission tomography/computed tomography (18F-PSMA-1007 PET-CT) was superior to the other imaging modalities studied for the detection of distant metastasis at the time of initial diagnosis of high-risk prostate cancer. PSMA PET-CT also appears to detect some nonmetastatic bone lesions.