Presentation Authors: Lorenzo Bianchi*, Francesco Ceci, Marco Borghesi, Giulia Polverari, Federico Mineo Bianchi, Umberto Barbaresi, Francesco Chessa, Paolo Castellucci, Riccardo Schiavina, Stefano Fanti, Eugenio Brunocilla, Bologna, Italy
Introduction: To develop a clinical nomogram to predict which patients with recurrent prostate cancer (PCa) could benefit from 68Gallium-Prostate Specific Membrane Antigen Positron Emission Tomography/Computed Tomography (68Ga-PSMA PET/CT).
Methods: We retrospectively enrolled 703 PCa patients with biochemical recurrence (BCR) after radical prostatectomy (n=684) and primary radiotherapy (n=19). Each man underwent 68Ga-PSMA PET/CT to identify site of recurrence. Patients were stratified according to: first PSA relapse (group 1 n=325), BCR after salvage therapy (group 2 n=241), PSA persistence after primary therapy (group 3 n=76) and disease progression before starting systemic therapies (group 4 n=61). We assessed the detection rate (DR) of 68Ga-PSMA PET/CT in overall population and in each subgroup. Multivariate logistic regressions were used to determine which co-variates (including ISUP group, PSA at 68Ga-PSMA PET/CT, PSA doubling time, ongoing androgen deprivation therapy [ADT] at 68Ga-PSMA PET/CT, time to recurrence and the clinical setting) independently predict a positive 68Ga-PSMA PET/CT. Regression-based coefficients were used to develop a nomogram predicting positive 68Ga-PSMA PET/CT and 200 bootstrap resamples were used for internal validation.
Results: Table 1: overall patients characteristics. Median PSA at 68Ga-PSMA PET/CT was 0.7 ng/ml (IQR 0.4- 1.3). Overall, 116 (16.5 %) men were on-going with ADT at 68Ga-PSMA PET/CT time. Median time to BCR was 21 months (IQR 9-49); median PSA doubling time was 6 months (IQR 4-10). The overall DR of 68Ga-PSMA PET/CT was 51.2 %. Table 2: PET/CT diagnostic performance among the different groups: DR was 40.3 %, 54 %, 60.5% and 86.9 % in group 1, 2, 3 and 4, respectively (p < 0.001). At multivariate analysis ISUP grade group, PSA at 68Ga-PSMA PET/CT, PSA doubling time and the clinical setting were independent predictors of positive 68Ga-PSMA PET/CT results (all pâ‰¤0.04). A nomogram based on covariates included in the multivariate model demonstrated bootstrap-corrected predictive accuracy of 82%.
Conclusions: Our nomogram could help physician to select patients with different scenario of recurrence who may benefit from 68Ga-PSMA PET/CT restaging.