Abstract
Despite the key-role of the Prostate Imaging and Reporting and Data System (PI-RADS) in the diagnosis and characterization of prostate cancer (PCa), this system remains to be affected by several limitations, primarily associated with the interpretation of equivocal PI-RADS 3 lesions and with the debated role of Dynamic Contrast Enhanced-Magnetic Resonance Imaging (DCE-MRI), which is only used to upgrade peripheral PI-RADS category 3 lesions to PI-RADS category 4 if enhancement is focal. We aimed at investigating the usefulness of radiomics for detection of PCa lesions (Gleason Score ≥ 6) in PI-RADS 3 lesions and in peripheral PI-RADS 3 upgraded to PI-RADS 4 lesions (upPI-RADS 4). Multiparametric MRI (mpMRI) data of patients who underwent prostatic mpMRI between April 2013 and September 2018 were retrospectively evaluated. Biopsy results were used as gold standard. PI-RADS 3 and PI-RADS 4 lesions were re-scored according to the PI-RADS v2.1 before and after DCE-MRI evaluation. Radiomic features were extracted from T2-weighted MRI (T2), Apparent diffusion Coefficient (ADC) map and DCE-MRI subtracted images using PyRadiomics. Feature selection was performed using Wilcoxon-ranksum test and Minimum Redundancy Maximum Relevance (mRMR). Predictive models were constructed for PCa detection in PI-RADS 3 and upPI-RADS 4 lesions using at each step an imbalance-adjusted bootstrap resampling (IABR) on 1000 samples. 41 PI-RADS 3 and 32 upPI-RADS 4 lesions were analyzed. Among 293 radiomic features, the top selected features derived from T2 and ADC. For PI-RADS 3 stratification, second order model showed higher performances (Area Under the Receiver Operating Characteristic Curve—AUC— = 80%), while for upPI-RADS 4 stratification, first order model showed higher performances respect to superior order models (AUC = 89%). Our results support the significant role of T2 and ADC radiomic features for PCa detection in lesions scored as PI-RADS 3 and upPI-RADS 4. Radiomics models showed high diagnostic efficacy in classify PI-RADS 3 and upPI-RADS 4 lesions, outperforming PI-RADS v2.1 performance.
Highlights
With the goal of standardizing the acquisition and reporting of prostatic Multiparametric MRI (mpMRI) imaging examinations, the European Society of Urogenital Radiology (ESUR) developed the Prostate Imaging-Reporting and Data System (PI-RADS) in 2013 and updated it in 2015 (PI-RADS v2) and 2019 (PI-RADS v2.1)[4]
Radiomic tool has been widely explored in the field of prostate cancer (PCa) and led to promising results, but especially in studies aiming at differentiating between normal and cancerous prostatic tissue, characterizing PCa lesions in terms of aggressiveness according to Gleason Score (GS), and comparing diagnostic power of radiomic features with that of Prostate Imaging and Reporting and Data System (PI-RADS) s coring[16,17,18,19,20,21,22]
For lesions evaluated as PI-RADS 3, PI-RADS reevaluation confirmed a PI-RADS 3 score in both biparametric MRI (bpMRI) and mpMRI reading session
Summary
With the goal of standardizing the acquisition and reporting of prostatic mpMRI imaging examinations, the European Society of Urogenital Radiology (ESUR) developed the Prostate Imaging-Reporting and Data System (PI-RADS) in 2013 and updated it in 2015 (PI-RADS v2) and 2019 (PI-RADS v2.1)[4]. Studies aimed at stratifying PI-RADS 3 lesions are limited[9,11,12,13,14,15] Another limitation directly affecting PI-RADS 3 lesion assignment concerns the role of DCE-MRI, which is still regarded as very controversial and debated, and its added value in combination with T2 and DWI was still not clearly assessed. Radiomic tool has been widely explored in the field of PCa and led to promising results, but especially in studies aiming at differentiating between normal and cancerous prostatic tissue, characterizing PCa lesions in terms of aggressiveness according to Gleason Score (GS), and comparing diagnostic power of radiomic features with that of PI-RADS s coring[16,17,18,19,20,21,22]. To our knowledge, only Giambelluca et al.[23] applied radiomic approach to stratify PI-RADS 3 lesions, and there are any studies aiming at investigating the power of radiomics in stratify PI-RADS 3 upgraded to PI-RADS 4
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