No abstract

Introduction: Conventional imaging (CI) performs poorly to identify sites of disease in biochemically recurrent prostate cancer. 68Ga-PSMA-11 positron emission tomography/ computed tomography (PET/CT) is most studied but has a very short half-life. This study reports the diagnostic performance of the novel prostate-specific membrane antigen (PSMA) radiotracer 18F-DCFPyL using real-life data, and tumor board simulation to estimate the impact of 18F-DCFPyL PET on patient management. Methods: Ninety-three 18F-DCFPyL PET/CT scans performed for patients previously treated for prostate cancer with a rising prostate-specific antigen (PSA) were retrospectively compared to contemporary CI, and clinical, imaging and PSA followups. A chart review was performed to document prior imaging, pathology results, serial serum PSA measurements, and other pertinent clinical data. Clinical utility of 18F-DCFPyL PET was measured using a simulated tumor board formed by three physicians with extensive prostate cancer experience deciding on management with and without knowledge of PET/CT results. Results: At median PSA 2.27 (interquartile range [IQR] 5.27], 82% of 18F-DCFPyL PET/CT demonstrated at least one site of disease: non-regional lymph nodes (37% of scans), regional lymph node metastases (28%), local recurrence (27%), bone metastases (20%), with higher PET positivity at higher PSA. Compared to 18F-DCFPyL PET/CT, CI showed overall poor performance, with accuracy below 20% for all extent of disease. PET/CT changed management in 44% of cases. The most frequent scenario was a radical change from initiating androgen deprivation therapy (ADT) to stereotactic body radiotherapy (SBRT) of oligo-lesional disease. In univariate and multivariate analysis, no patient characteristic could predict change of management by PET/CT results. Conclusions: 18F-DCFPyL significantly outperforms CI in recurring prostate cancer and is likely to impact management.

A 69-year-old man with biochemical recurrence after radical prostatectomy underwent 6 months of androgen deprivation therapy. Upon discontinuation of androgen deprivation therapy, serum prostate-specific antigen rose again to 0.69 ng/mL, and 18F-DCFPyL PET/CT was performed to identify the site of recurrence. However, only an intense focus of uptake in the spleen could be found. Subsequent contrast-enhanced MRI findings were pathognomonic for splenic hemangioma.

Introduction: We sought to evaluate the diagnostic performance of 18F-fluorocholine positron emission tomography-computed tomography (18F-FCH PET/CT) for initial staging of patients with high-risk prostate cancer. Secondary objectives were to compare the value of 18F-FCH PET/CT to conventional imaging modalities and to evaluate its clinical impact. Methods: We conducted a retrospective study of 76 patients who underwent 18F-FCH PET/CT for initial staging of high-risk prostate cancer. Using pre-established validation criteria, sensitivity and specificity were determined for metastatic disease. Results were compared to findings on magnetic resonance imaging (MRI), computed tomography (CT), and bone scan (BS) when available. Results: Twenty-two (29%) PET/CT scans were positive, 49 (64%) negative, and five (7%) equivocal for nodal or metastatic disease. Of the positive scans, 17 showed regional lymph node involvement, 12 distant nodes, five bone metastases, and three lung metastases. Overall per-patient sensitivity, specificity, positive and negative predictive values for metastatic disease were 65%, 100%, 100%, and 78%, respectively. Sensitivity, specificity, and positive and negative predictive values were 64%, 100%, 100%, and 80%, respectively, for nodal involvement and 86%, 100%, 100%, and 98%, respectively, for bone and other metastases. Conventional imaging was negative for the lesion(s) found on PET/CT in five patients. PET/CT changed the clinical management in nine patients (12%). Conclusions: Although 18F-FCH PET/CT offers some benefits over conventional imaging and demonstrates a high specificity, it remains limited by its sensitivity in the context of high-risk prostate cancer staging. PET with novel urea-based small molecule prostate-specific membrane antigen (PSMA) inhibitors may overcome some of these limitations. However, the interpretation of the study result is limited by the lack of available histological gold standard, the inclusion of several patients who received androgen-deprivation therapy (ADT) prior to PET/CT, our retrospective design, and a relatively small sample size.