68Ga-PSMA-11 PET/CT in recurrent prostate cancer: efficacy in different clinical stages of PSA failure after radical therapy
The primary objective was the evaluation of Gallium 68 (68Ga)-prostate-specific membrane antigen (PSMA)-11 positron emission tomography/computed tomography (PET/CT) detection rate, for identifying the site of prostate cancer (PCa) relapse (local vs systemic), stratifying the population according to different clinical stages of biochemical recurrence (BCR). Secondary aims were: 1) to evaluate the association of clinical/pathologic features and 68Ga-PSMA-11 PET/CT detection rate, 2) to compare 68Ga-PSMA-11 PET/CT with other imaging procedures, and 3) to evaluate the positive predictive value (PPV) in a per-patient analysis.
Material and methods
This population was enrolled through a prospective, open label, single-center trial performed at the Nuclear Medicine of the University Hospital of Bologna (Eudract: 2015-004589-27 OsSC). The inclusion criteria were: (1) proven PCa, (2) surgery or radiotherapy as definitive therapy, (3) proven BCR, (4) prostate-specific antigen (PSA) 0.2–2 ng/ml, (5) age ≥ 35 years, and 6() willing to sign an informed consent. Three-hundred and thirty-two (332) patients were enrolled between March 2016 and June 2017; mean/median PSA was 0.84/0.61 ng/ml, 97.9% (325/332) of patients received radical prostatectomy and 2.1% (7/332) radiotherapy. Different patterns of BCR were identified by referent physicians as follows: (a) persisting detectable PSA after radical prostatectomy in 13.5% (45/332) of patients (subgroup 1), (b) first-time PSA failure after radical therapy in 44.9% (149/332) (subgroup 2), and (c) PSA increase after salvage or hormonal therapy in 41.6% (138/332) (subgroup 3).
Primary objective: 68Ga-PSMA-11 PET/CT detection rate was 53.6% (CI 95% 48.1%–59.1%). In a patient-based analysis, disease confined to pelvis (prostate bed and/or lymph-nodes) was detected in 24.7% of cases (82/332). The presence of at least one distant lesion was observed in 28.9% of cases (96/332). The detection rate in different subgroups was: subgroup 1 = 64.5%, subgroup 2 = 45.6%, and subgroup-3 = 58.7%. Secondary objectives: 1) PSA (p = 0.041) and PSAdt (p = 0.001) showed association with 68Ga-PSMA-11 PET/CT detection rate, and 2) correlative imaging was available in 73.2% of patients (243/332). When 68Ga-PSMA-11 PET/CT was positive, correlative imaging resulted negative in 83% of cases (108/130). 3) The calculated PPV was 96.2%.
Our data confirmed the efficacy of 68Ga-PSMA-11 PET/CT for detecting local vs systemic disease in PCa patients presenting PSA failure after radical therapy. Furthermore, 68Ga-PSMA-11 PET/CT detection rate is different depending on the clinical stage of BCR, and this information should be taken into consideration by referring physicians.
KeywordsPSMA PET/CT Biochemical recurrence Prostate cancer PSMA prostate PSMA prospective First biochemical recurrence
Francesco Ceci is supported by a Postdoctoral Fellowship Award from the Fondazione Umberto Veronesi (Post-doctoral Travel-Grant 2018) for his research at University of California Los Angeles (UCLA), about theranostic applications of PSMA inhibitors in prostate cancer.
Compliance with ethical standards
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the principles of the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
Conflict of interest
Authors declare no conflict of interest.
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