A Multicenter Prospective Clinical Trial of 68Gallium PSMA HBED-CC PET-CT Restaging in Biochemically Relapsed Prostate Carcinoma: Oligometastatic Rate and Distribution Compared With Standard Imaging.

<bold>Purpose: </bold>The purpose of this study is to assess the utility of 68Gallium prostate-specific membrane antigen (PSMA) Division of Radiopharmaceutical Chemistry (DKFZ)-PSMA-11 positron emission tomography (PET)-computed tomography (CT), compared with standard imaging, in the detection of recurrent prostate carcinoma in patients with biochemical relapse to determine the prevalence of oligometastatic disease recurrence and its distribution.<bold>Methods and Materials: </bold>This is a prospective, multicenter clinical trial of PSMA-HBED PET/CT imaging in patients with early biochemical relapse of prostate carcinoma (median prostate-specific antigen [PSA], 2.55 ng/mL) after definitive prostatectomy (152 patients) or radiation therapy (86 patients) with either no lesions or oligometastatic disease on abdominopelvic CT and bone scan (BS). PSMA-HBED PET/CT scan was performed within 8 weeks of restaging imaging, and all sites of abnormal PSMA-HBED binding determined as probable or definite for prostate carcinoma were included in the analysis. PSMA positivity was assessed for correlation with Gleason Score, PSA level, and PSA doubling time.<bold>Results: </bold>Two hundred thirty-eight patients underwent PSMA-HBED PET/CT imaging. In 199 patients with no lesions on restaging CT and BS, 148 patients (74%) demonstrated PSMA-positive lesions, with 113 patients (57%) being oligometastatic. In 39 patients with oligometastatic lesions on restaging CT and BS, 19 patients (49%) were confirmed as oligometastatic on PSMA PET/CT and 16 patients (41%) were upstaged to polymetastatic. The 4 remaining patients (10%) with sites of possible metastatic disease were not confirmed as having prostate carcinoma. Combining the overall group, there were 183 patients (77%) with PSMA-HBED-positive lesions (682 lesions), suggesting prostate carcinoma, of whom 132 patients (55%) were oligometastatic. In the oligometastatic group, PSMA positivity was limited to the pelvis in 65% of patients, involving either the prostate or nodes (American Joint Committee on Cancer stage N1). This study found a positive correlation between PSMA-HBED positivity and PSA levels; no other factors were statistically significant.<bold>Conclusions: </bold>For patients with biochemical relapse with BS and CT demonstrating either no disease or low-volume disease, there is a high overall prevalence of PSMA PET/CT-positive disease. More than half of the patients were oligometastatic, and of those, disease was confined to the pelvis in nearly two-thirds of patients. This result confirms that PSMA PET/CT is significantly more sensitive than standard restaging imaging, and it may be useful in identifying patients for subsequent targeted therapy. [ABSTRACT FROM AUTHOR]