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.

Abstract

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. 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. 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. 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.