DISCUSSION
PCa accounts for 25% of malignancies newly diagnosed every year in Europe (5). The multiparametric approach is essential for detecting and characterizing PCa. PCa prognosis is closely related to cancer stage. In this context, MRI plays a critical role in staging, which is important in PCa management. The presence of EPE impacts TNM staging by increasing the T-stage from 2 to 3 and significantly increases the risk of biochemical recurrence in postoperative follow-up (6).
In the literature, there are several studies evaluating the effectiveness of MRI in detecting EPE(Table 6). According to the results obtained in these studies, MRI sensitivity in detecting EPE fluctuated in a wide range (40%‒84%), but its specificity was as high as 97%. Furthermore, a few recent publications on TCL(4,7–10) have emerged. In these studies, no consensus wasestablished on the threshold value for TCL, which varied in a wide range of 6‒20 mm. However, PI-RADS v2, published by ACR in 2015 and used in the preparation of prostate MRI reports in many healthcare centers, recommends acceptance of a threshold value of 10 mm for TCL when evaluating EPE (7). Even though ACR revised it as PI-RADS v2.1, there are no new recommendations for TCL (11).
In Rosenkrantz et al. (4), preoperative 3T MRI images of 90 patients who underwent radical prostatectomywere assessed. The evaluation was made on T2W and ADC images. The threshold values for TCL were determinedas 6 mm for T2W and 7 mm for ADC.
Woo et al. (9) performed a study regarding EPE on 3T MRI images with one observer in 2016. T2W, ADC, and DCE images were evaluated, and the threshold values of TCL were 14, 13, and 12 mm, respectively. No statistically significant difference was found between the sequences. The statistical workup, in which all sequences were evaluated together, yielded a threshold value of 14 mm. Furthermore, the clinicalstage, PSA, and Gleason score were found to be significantly correlated with the presence of EPE.
In a study conducted by Costa et al. in 2018 (12), the efficiency of 3T MRI using an endorectal coil in the detection of EPEwas examined, and it was observedthat a TCL higher than 10 mm increased the probability of EPE by 2.4 times.
Bakır et al. performed one of the most recent studies on this topic in 2020(10). The 3T MRI of 86 patients were evaluated,and the relationship between TCL and EPE using the MRI-based TCL measurements and the real TCL measurements from pathology were assessed. According to the MR-based TCL measurements, a cutoff value of 15–16 mm was obtained. However, there was no significant relationship between pathology-based TCL measurements and EPE. It was concluded that MRI-based TCL measurements may be beneficial in predicting EPE.
There are a limited number of studies that use 1.5T MR for evaluation (8,13,14). The threshold values for TCL were mentioned as 14 and 20 mm in these publications.
In our study, it was observed that the increased PI-RADS score was significantly correlated with the presence of EPE, as well as increased Gleason score and ISUP grade. On the other hand, LL and TCL were significantly correlated with the presence of EPE. Moreover, in the histopathological and radiological examinations, a cutoff value was observed for LL. Likewise, a cutoff value for the radiological TCL was observed concerning EPE. Considering these data, it is thought that the LL and the TCL maybe used as an auxiliary in the detection of EPE while evaluating MRI images.
Unlike in the other studies, we evaluated bothradiologic and histopathologic LL along with TCL for the detection of EPE. Furthermore, we used the most recent version of the PI-RADS (v2.1) while evaluating mpMRI.On the other hand, most of these studies were performed using 3T MRI scanners. Endorectal coils were also utilized in some cases. In our study, we evaluated the effectiveness of the mpMRI obtained with a 1.5T MR device without an endorectal coil, which is a commonly used method in many centers for EPE detection. Furthermore, in 15 lesions without capsule contact, which were mentioned in the exclusion criteria, pathological capsule invasion was not observed. Studies evaluating the relationship between the distance to the capsule and pathological EPE in such lesions may yield more reliable results.
There were some limitations to the study design. The number of patients was limited, since only patients who underwent radical prostatectomy were enrolled.Although we could not compare 1.5T and 3T methods in detecting EPE,there are yet no studies in the literature that provide such comparisons. The evaluation of TCL was made only radiologically, and this fact might be accepted as another limiting factor. Histopathological assessment of TCL may shed more light on this topic.