Peripheral zone lesions of intermediary risk in multiparametric prostate MRI: Frequency and validation of the PI-RADSv2 risk stratification algorithm based on focal contrast enhancement

Correlation between Intraprostatic PSMA Uptake and MRI PI-RADS of [68Ga]Ga-PSMA-11 PET/MRI in Patients with Prostate Cancer: Comparison of PI-RADS Version 2.0 and PI-RADS Version 2.1

PURPOSE

We aimed to evaluate the correlation between PSMA uptake and magnetic resonance imaging (MRI) PI-RADS of simultaneous [⁶⁸Ga]Ga-PSMA-11 PET/MRI regarding PI-RADS version 2.0 and 2.1 respectively and compared the difference between these two versions.

MATERIALS AND METHODS

We retrospectively analyzed a total of forty-six patients with biopsy-proven prostate cancer who underwent simultaneous [⁶⁸Ga]Ga-PSMA-11 PET/MRI. We classified the lesions regarding PI-RADS version 2.0 and 2.1, peripheral zone (PZ), and transitional zone (TZ), respectively. Based on regions of interest (ROI), standardized uptake values maximum (SUVmax), and corresponding lesion-to-background ratios (LBR) of SUVmax of each category, PI-RADS score 1 to 5, were measured. A comparison between PI-RADS version 2.0 and PI-RADS version 2.1 was performed.

RESULTS

A total of 215 focal prostate lesions were analyzed, including two subgroups, 125 TZ and 90 PZ. Data are reported as median and interquartile range (IQR). Regarding PI-RADS version 2.1, TZ SUVmax of each category were 1.5 (0.5, 1.9), 1.9 (0.8, 2.3), 3.3 (2.1, 4.6), 4.2 (3.1, 5.7), 7.3 (5.2, 9.7). PZ SUVmax of each category were 1.0 (0.8, 1.6), 2.5 (1.5, 3.2), 3.3 (1.9, 4.5), 4.3 (3.0, 5.4), 7.4 (5.0, 9.3). Regarding the inter-reader agreement of the overall PI-RADS assessment category, the kappa value was 0.723 for version 2.0 and 0.853 for version 2.1.

CONCLUSION

Revisions of PI-RADS version 2.1 results in variations in lesions classification. Lesions with the PI-RADS category of 3, 4, and 5 present relatively higher intraprostatic PSMA uptake, while lesions with the PI-RADS category of 1 and 2 present relatively lower and similar uptake. Version 2.1 has higher inter-reader reproducibility than version 2.0.

Association Between Tumor Multifocality on Multi-parametric MRI and Detection of Clinically-Significant Prostate Cancer in Lesions with Prostate Imaging Reporting and Data System (PI-RADS) Score 4

OBJECTIVE

To investigate whether presence of multifocality on multi-parametric magnetic resonance imaging would increase the likelihood of detecting clinically-significant prostate cancer in a PI-RADS 4 lesion.

METHODS

We identified patients with at least 1 PI-RADS 4 lesion who underwent multi-parametric magnetic resonance imaging-ultrasound fusion prostate biopsy. Patients were grouped into 1 of 4 cohorts-cohort 1 (a PI-RADS 4 index lesion and an additional PI-RADS 2 or 3 lesion), cohort 2 (single lesion with PI-RADS 4), cohort 3 (2 or more PI-RADS 4 lesions), or cohort 4 (a PI-RADS 4 lesion and an index lesion with PI-RADS 5). We compared the rate of grade group (GG) ≥ 2 pathology on targeted biopsy of PI-RADS 4 lesions between cohorts and evaluated clinical and radiological factors associated with cancer detection.

RESULTS

The overall rate of GG ≥ 2 pathology in the PI-RADS 4 lesions was 35.2%. The rate of GG ≥ 2 pathology in the cohorts 1, 2, 3, and 4 was 21.7%, 36.3%, 49.1%, and 42.7%, respectively (P< .001). On multivariable analysis, age (OR1.06, P < .001), clinical stage T2 (OR1.59, P= .03), prostate-specific antigen density (OR1.43, P < .001), peripheral zone lesion (OR1.62, P = .04), and study cohort (cohort 2 vs 1, OR1.93, P = .006; and cohort 3 vs 1, OR3.28, P < .001) were significantly associated with the risk of GG ≥ 2 in the PI-RADS 4 lesion.

CONCLUSION

On targeted biopsy of the PI-RADS 4 lesions, the proportion of GG ≥ 2 pathology is approximately 35%. Rate of GG ≥ 2 detection in PI-RADS 4 lesions might differ based on their location, multifocality, and PI-RADS classifications of other lesions identified.

Comparison of PI-RADS version 2 and PI-RADS version 2.1 for the detection of transition zone prostate cancer

PURPOSE

To compare the diagnostic performance of PI-RADS v2 and v2.1 for detecting transition zone prostate cancer (TZPC) on multiparametric prostate MRI (mpMRI).

METHOD

Fifty-eight patients with elevated PSA levels underwent mpMRI at 3 T including T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI), and subsequent MRI-transrectal ultrasonography fusion-guided prostate-targeted biopsy (MRGB). The standard of reference was MRGB-derived histopathology. Two readers independently assessed each TZ lesion, assigning a score of 1-5 for T2WI, a score of 1-5 for DWI, and the overall PI-RADS assessment category according to PI-RADS v2 and v2.1. The diagnostic performance of the two methods was compared in terms of inter-reader agreement, diagnostic sensitivity, diagnostic specificity, and area under the ROC curve (AUC).

RESULTS

Of the 58 patients, 26 were diagnosed with PC (GS = 3 + 3, n = 9; GS = 3 + 4, n = 9; GS = 3 + 5, n = 1; GS = 4 + 3, n = 4; GS = 4 + 4, n = 3) and 32 with benign lesions. Regarding inter-reader agreement of overall PI-RADS assessment category, the kappa value was 0.580 for v2 and 0.645 for v2.1. For both readers, there was no difference in diagnostic sensitivity between the versions (p ≥ 0.500). For reader 1, the diagnostic specificity was higher for v2.1 (p = 0.002), and was similar for reader 2 (p = 1.000). For both readers, AUC tended to be higher for v2.1 than for v2, but the difference was not significant (0.786 vs. 0.847 for reader 1, p = 0.052; and 0.808 vs. 0.858 for reader 2, p = 0.197).

CONCLUSIONS

These results suggest that compared with PI-RADS v2, PI-RADS v2.1 could be preferable for evaluating TZ lesions.

Evolution of prostate MRI: from multiparametric standard to less-is-better and different-is better strategies

Multiparametric magnetic resonance imaging (mpMRI) has become the standard of care to achieve accurate and reproducible diagnosis of prostate cancer. However, mpMRI is quite demanding in terms of technical rigour, patient's tolerability and safety, expertise in interpretation, and costs. This paper reviews the main technical strategies proposed as less-is-better solutions for clinical practice (non-contrast biparametric MRI, reduction of acquisition time, abbreviated protocols, computer-aided diagnosis systems), discussing them in the light of the available evidence and of the concurrent evolution of Prostate Imaging Reporting and Data System (PI-RADS). We also summarised research results on those advanced techniques representing an alternative different-is-better line of the still ongoing evolution of prostate MRI (quantitative diffusion-weighted imaging, quantitative dynamic contrast enhancement, intravoxel incoherent motion, diffusion tensor imaging, diffusional kurtosis imaging, restriction spectrum imaging, radiomics analysis, hybrid positron emission tomography/MRI).

Imaging as a Personalized Biomarker for Prostate Cancer Risk Stratification

Biomarkers provide objective data to guide clinicians in disease management. Prostate-specific antigen serves as a biomarker for screening of prostate cancer but has come under scrutiny for detection of clinically indolent disease. Multiple imaging techniques demonstrate promising results for diagnosing, staging, and determining definitive management of prostate cancer. One such modality, multiparametric magnetic resonance imaging (mpMRI), detects more clinically significant disease while missing lower volume and clinically insignificant disease. It also provides valuable information regarding tumor characteristics such as location and extraprostatic extension to guide surgical planning. Information from mpMRI may also help patients avoid unnecessary biopsies in the future. It can also be incorporated into targeted biopsies as well as following patients on active surveillance. Other novel techniques have also been developed to detect metastatic disease with advantages over traditional computer tomography and magnetic resonance imaging, which primarily rely on defined size criteria. These new techniques take advantage of underlying biological changes in prostate cancer tissue to identify metastatic disease. The purpose of this review is to present literature on imaging as a personalized biomarker for prostate cancer risk stratification.