Supervised machine learning enables non-invasive lesion characterization in primary prostate cancer with [ 68 Ga]Ga-PSMA-11 PET/MRI.

Purpose: Risk classification of primary prostate cancer in clinical routine is mainly based on prostate-specific antigen (PSA) levels, Gleason scores from biopsy samples, and tumor-nodes-metastasis (TNM) staging. This study aimed to investigate the diagnostic performance of positron emission tomography/magnetic resonance imaging (PET/MRI) in vivo models for predicting low-vs-high lesion risk (LH) as well as biochemical recurrence (BCR) and overall patient risk (OPR) with machine learning.
Methods: Fifty-two patients who underwent multi-parametric dual-tracer [ ¹⁸ F]FMC and [ ⁶⁸ Ga]Ga-PSMA-11 PET/MRI as well as radical prostatectomy between 2014 and 2015 were included as part of a single-center pilot to a randomized prospective trial (NCT02659527). Radiomics in combination with ensemble machine learning was applied including the [ ⁶⁸ Ga]Ga-PSMA-11 PET, the apparent diffusion coefficient, and the transverse relaxation time-weighted MRI scans of each patient to establish a low-vs-high risk lesion prediction model (M _LH ). Furthermore, M _BCR and M _OPR predictive model schemes were built by combining M _LH , PSA, and clinical stage values of patients. Performance evaluation of the established models was performed with 1000-fold Monte Carlo (MC) cross-validation. Results were additionally compared to conventional [ ⁶⁸ Ga]Ga-PSMA-11 standardized uptake value (SUV) analyses.
Results: The area under the receiver operator characteristic curve (AUC) of the M _LH model (0.86) was higher than the AUC of the [ ⁶⁸ Ga]Ga-PSMA-11 SUV _max analysis (0.80). MC cross-validation revealed 89% and 91% accuracies with 0.90 and 0.94 AUCs for the M _BCR and M _OPR models respectively, while standard routine analysis based on PSA, biopsy Gleason score, and TNM staging resulted in 69% and 70% accuracies to predict BCR and OPR respectively.
Conclusion: Our results demonstrate the potential to enhance risk classification in primary prostate cancer patients built on PET/MRI radiomics and machine learning without biopsy sampling.