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BACKGROUND AND OBJECTIVE: Multiparametric magnetic resonance imaging (mpMRI) of the prostate is used for prostate cancer diagnosis. However, mpMRI has lower sensitivity for small tumours. Prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA-PET/CT) offers increased sensitivity over conventional imaging. This study aims to determine whether the diagnostic accuracy of 18F-DCFPyL PSMA-PET/CT was superior to that of mpMRI for detecting prostate cancer (PCa) at biopsy. METHODS: Between 2020 and 2021, a prospective multicentre single-arm phase 3 imaging trial enrolled patients with clinical suspicion for PCa to have both mpMRI and PSMA-PET/CT (thorax to thigh), with reviewers blinded to the results of other imaging. Multiparametric MRI was considered positive for Prostate Imaging Reporting and Data System (PIRADS) 3-5. PSMA-PET/CT was assessed quantitatively (positive maximum standardised uptake value [SUVmax] >7) and qualitatively (five-point lexicon of certainty). Patients underwent targeted and systematic biopsy, with the technique at the discretion of the treating urologist. Clinically significant PCa (csPCa) was defined as International Society of Urological Pathology grade group (GG) ≥2. The primary outcome was the diagnostic accuracy for detecting PCa, reported as sensitivity, specificity, negative predictive value (NPV), and area under the curve (AUC) of the receiver operating curve. The secondary endpoints included a comparison of the diagnostic accuracy for detecting csPCa, assessing gains in combining PMSA-PET/CT with mpMRI to mpMRI alone. KEY FINDINGS AND LIMITATIONS: Of the 236 patients completing both mpMRI and PSMA-PET/CT, 184 (76.7%) had biopsy. Biopsy histology was benign (n = 73), GG 1 (n = 27), and GG ≥2 (n = 84). The diagnostic accuracy of mpMRI for detecting PCa (AUC 0.76; 95% confidence interval [CI] 0.69, 0.82) was higher than that of PSMA-PET/CT (AUC 0.63; 95% CI 0.56, 0.70, p = 0.03). The diagnostic accuracy of mpMRI for detecting csPCa (AUC 0.72; 95% CI 0.67, 0.78) was higher than that of PSMA-PET/CT (AUC 0.62; 95% CI 0.55, 0.69) but not statistically significant (p = 0.27). A combination of PSMA-PET/CT and mpMRI showed excellent sensitivity (98.8%, 95% CI 93.5%, 100%) and NPV (96%, 95% CI 79.6%, 99.9%) over mpMRI alone (86.9% and 80.7%, respectively, p = 0.01). Thirty-two patients (13.6%) had metastatic disease. They tended to be older (68.4 vs 65.1 yr, p = 0.023), and have higher prostate-specific antigen (PSA; median PSA 9.6 vs 6.2ng/ml, p < 0.001) and abnormal prostate on digital rectal examination (78.2% vs 44.1%, p < 0.001). CONCLUSIONS AND CLINICAL IMPLICATIONS: Multiparametric MRI had superior diagnostic accuracy to PSMA-PET/CT for detecting PCa, though the difference is not significant in case of csPCa detection. A combination of mpMRI and PSMA-PET/CT showed improved sensitivity and NPV. PSMA-PET/CT could be considered for diagnostic use in patients unable to have mpMRI or those with concerning clinical features but negative mpMRI. PATIENT SUMMARY: In this trial, we compared the ability of 18F-labelled prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA-PET/CT) with that of multiparametric magnetic resonance imaging (mpMRI) to diagnose prostate cancer by biopsy in a prostate-specific antigen screening population. We found that MRI was superior to PSMA to diagnose prostate cancer, though there was no difference in ability to diagnose clinically significant prostate cancer. PSMA-PET/CT could be considered for diagnostic use in patients unable to have mpMRI or those with concerning clinical features but negative mpMRI. Combining MRI with PSMA-PET increases the negative predictive value over MRI alone and may help men avoid invasive prostate biopsy.
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Background: Prostate-specific membrane antigen (PSMA) positron emission tomography/computerised tomography (PET/CT) is increasingly being utilised in the diagnostic pathway for prostate cancer (PCa). Recent publications have suggested that this might help identify those who can avoid biopsy. Objective: The primary objective of this study was to determine whether PET magnetic resonance imaging (MRI) fusion could negate the need to biopsy prior to prostatectomy in a selected population of men. Design setting and participant: Multiparametric MRI (mpMRI) for PCa is our standard of care prior to prostate biopsy. Biopsy-naïve men with one or more Prostate Imaging Reporting and Data System (PI-RADS) 4 or 5 lesions ≥10 mm on mpMRI were invited to undergo PSMA PET/CT prior to biopsy. Following ethics approval, 60 men were recruited between September 2020 and March 2021. The key exclusion criteria included a previous history of PCa and previous prostate surgery or biopsy. Outcome measurements and statistical analysis: A positive PET MRI fusion scan was defined as "consistent with" as per the Memorial Sloan Kettering Cancer Center lexicon of certainty, and concordance with biopsy results was analysed. Clinically significant PCa (csPCa) was defined as grade group (GG) ≥2 on pathology. A chi-square analysis was performed with statistical significance defined at p < 0.05. Results and limitations: A total of 71 mpMRI lesions were positive on 61 (86%) PET MRI fusion scans. Fifty-nine of 61 lesions biopsied confirmed csPCa in 54 (92%). Of five of 59 lesions for which either biopsy was negative or low-grade cancer was found, three had rebiopsy of which two were confirmed to have csPCa corroborating with PET MRI fusion and one was reconfirmed to have GG1 only. For the remaining two, both had another lesion elsewhere in the gland confirming csPCa, and hence rebiopsy was not performed. Ultimately, 56 of 59 (95%) lesions with a positive PET MRI fusion scan were confirmed to have csPCa. All GG ≥3 cancers had a positive PET MRI fusion scan. Conclusions: This prospective study of PET MRI fusion assessment of men with PI-RADS 4 or 5 lesion ≥10 mm on mpMRI confirms that the majority of men (95%) with a positive PET MRI fusion scan will have csPCa. This supports recently published retrospective data suggesting that selected men might avoid prostate biopsy prior to radical prostatectomy. Patient summary: In this research, we have confirmed that prostate-specific membrane antigen positron emission tomography/computerised tomography in combination with magnetic resonance imaging could have an important role in enabling a diagnosis of prostate cancer. Using the combination of these scans, we could confidently predict the presence of aggressive prostate cancer in some men for which treatment is warranted. This means that there are some men who could possibility proceed directly to having prostate cancer surgery without the need for a confirmatory prostate biopsy.
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