Diagnostic performance of Ga-PSMA-11 PET/MRI in biochemical recurrent prostate cancer after radical prostatectomy and prediction nomogram.

Background: This study aimed to evaluate the diagnostic performance of Ga-PSMA-11 PET/MRI in prostate cancer (PC) with biochemical recurrence (BCR) after radical prostatectomy (RP). It was also aimed to develop a nomogram to predict PET/MRI positivity.

Methods: The data of 140 PC patients who underwent Ga-PSMA-11 PET/MRI for BCR after RP were retrospectively analyzed. PSA, ISUP Gleason grades (GG), androgen deprivation therapy (ADT), and PSA doubling time (PSAdt) were recorded. Regression analysis was performed to determine the predictive factors for PET/MRI positivity. Regression coefficients were used to develop a nomogram in early BCR group (PSA < 1.0 ng/ml) and 100 bootstrap resamples were used for internal validation. Receiver operating characteristic analysis was used to evaluate the performance of model. Decision curve analysis (DCA) was implemented to quantify the clinical net benefit of nomogram.

Results: The overall detection rate was 75%. Detection rate was 100% in patients with PSA ≥ 1.0 ng/ml. In patients with early BCR (PSA < 1.0 ng/ml; n = 94), the detection rate was 62.8%. Prediction nomogram demonstrated a bootstrap corrected accuracy of 83%. In DCA, with a nomogram derived probability threshold ≥60%, the use of the nomogram would result in a net benefit gain of 36%.

Conclusions: If PSA level is ≥1.0 ng/ml in PC patients with BCR after RP, Ga-PSMA-11 PET/MRI has very high detection rates. In patients with PSA < 1.0 ng/ml, PSAdt seems to be the strongest predictive factor in the prediction of imaging positivity. Our nomogram provided good accuracy and it seems as an important tool in the best use of PET/MRI.