UCSF

Purpose

Prostate specific membrane antigen-targeted positron emission tomography/computerized tomography has the potential to improve the detection and localization of prostate cancer. OSPREY was a prospective trial designed to determine the diagnostic performance of ¹⁸F-DCFPyL-positron emission tomography/computerized tomography for detecting sites of metastatic prostate cancer.

Materials and methods

Two patient populations underwent ¹⁸F-DCFPyL-positron emission tomography/computerized tomography. Cohort A enrolled men with high-risk prostate cancer undergoing radical prostatectomy with pelvic lymphadenectomy. Cohort B enrolled patients with suspected recurrent/metastatic prostate cancer on conventional imaging. Three blinded central readers evaluated the ¹⁸F-DCFPyL-positron emission tomography/computerized tomography. Diagnostic performance of ¹⁸F-DCFPyL-positron emission tomography/computerized tomography was based on imaging results compared to histopathology. In cohort A, detection of pelvic nodal disease (with specificity and sensitivity as co-primary end points) and of extrapelvic metastases were evaluated. In cohort B, sensitivity and positive predictive value for prostate cancer within biopsied lesions were evaluated.

Results

A total of 385 patients were enrolled. In cohort A (252 evaluable patients), ¹⁸F-DCFPyL-positron emission tomography/computerized tomography had median specificity of 97.9% (95% CI: 94.5%-99.4%) and median sensitivity of 40.3% (28.1%-52.5%, not meeting prespecified end point) among 3 readers for pelvic nodal involvement; median positive predictive value and negative predictive value were 86.7% (69.7%-95.3%) and 83.2% (78.2%-88.1%), respectively. In cohort B (93 evaluable patients, median prostate specific antigen 11.3 ng/ml), median sensitivity and positive predictive value for extraprostatic lesions were 95.8% (87.8%-99.0%) and 81.9% (73.7%-90.2%), respectively.

Conclusions

The primary end point for specificity was met while the primary end point for sensitivity was not. The high positive predictive value observed in both cohorts indicates that ¹⁸F-DCFPyL-positive lesions are likely to represent disease, supporting the potential utility of ¹⁸F-DCFPyL-positron emission tomography/computerized tomography to stage men with high-risk prostate cancer for nodal or distant metastases, and reliably detect sites of disease in men with suspected metastatic prostate cancer.