A nomogram has recently been developed to predict 68Ga-labeled prostate-specific membrane antigen (PSMA)-11 positron emission tomography (PET)/computed tomography (PSMA-PET) results in recurrent prostate cancer (PCa) patients.
To perform external validation of the original nomogram in a multicentric setting.
A total of 1639 patients who underwent PSMA-PET for prostate-specific antigen (PSA) relapse after radical therapy were retrospectively included from six high-volume PET centers. The external cohort was stratified according to clinical setting categories: group 1: first-time biochemical recurrence (n = 774); group 2: PSA relapse after salvage therapy (n = 499); group-3: biochemical persistence after radical prostatectomy (n = 210); and group-4: advanced-stage PCa before second-line systemic therapies (n = 124).
PSMA-PET in recurrent PCa.
PSMA-PET detection rate was assessed in the overall population and in each subgroup. A multivariable logistic regression model was produced to evaluate the predictors of a positive scan. The performance characteristics of the model were assessed by quantifying the predictive accuracy (PA) according to model calibration. The Youden's index was used to find the best nomogram's cutoff. Decision curve analysis (DCA) was implemented to quantify the nomogram's clinical net benefit.
In the external cohort, the overall detection rate was 53.8% versus 51.2% in the original population. At multivariate analysis, International Society of Urological Pathology grade group, PSA, PSA doubling time, and clinical setting were independent predictors of a positive scan (all p ≤ 0.02). The PA of the nomogram was identical to the original model (82.0%); the model showed an optimal calibration curve. The best nomogram's cutoff was 55%. In the DCA, the nomogram revealed clinical net benefit when the threshold nomogram probabilities were ≥20%. The retrospective design is a major limitation.
The original nomogram exhibited excellent characteristics on external validation. The incidence of a false negative scan can be reduced if PSMA-PET is performed when the predicted probability is ≥20%.
A nomogram has been developed to predict prostate-specific membrane antigen/positron emission tomography (PSMA-PET) results for recurrent prostate cancer (PCa). The nomogram represents an easy tool in the decision-making process of recurrent PCa.
European urology oncology. 2021 Dec 18 [Epub ahead of print]
Lorenzo Bianchi, Paolo Castellucci, Andrea Farolfi, Matteo Droghetti, Carlos Artigas, Jose Leite, Paola Corona, Qaid Ahmed Shagera, Renata Moreira, Christian González, Marcelo Queiroz, Felipe de Galiza Barbosa, Riccardo Schiavina, Desiree Deandreis, Stefano Fanti, Francesco Ceci
Division of Urology, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy; Università degli studi di Bologna, Bologna, Italy., Division of Nuclear Medicine, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy., Division of Nuclear Medicine, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy. Electronic address: ., Division of Urology, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy., Department of Nuclear Medicine, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium., PET/CT Center, DASA - Diagnósticos da Améric, Rio de Janeiro, Brazil., Fundación Centro Diagnóstico Nuclear (FCDN), Buenos Aires, Argentina., Department of Radiology, Hospital Sírio-Libanês, University of Sao Paulo, Sao Paulo, Brazil., Nuclear Medicine, Department of Medical Sciences, University of Turin, Turin, Italy., Division of Nuclear Medicine and Theranostics, IEO European Institute of Oncology IRCCS, Milan, Italy.