MATERIAL AND METHODS
In this retrospectively designed study, 201cases who underwent radical prostatectomy performed at our institution between May 2014 and August 2017 were scanned. Of these, 130 cases who met the inclusion criteria were enrolled. The study was conducted afterobtaining approval from the ethics committee. The inclusion and exclusion criteria of the study are provided in the following segment.
Inclusion criteria for the included cases utilized in this study were as follows:
-Underwent radical prostatectomy
-Prostate malignancy detected by postsurgical histopathologic examination
-PI-RADS category 3, 4, or 5 lesions revealed by preoperative mpMRI
-Radiologically visible contact between the tumor and capsule
The exclusion criteria for cases were as follows:
-No preoperative MRI examination performed at our institution (18)
-No findings except PI-RADS 1 or 2 category on preoperative mpMRI (14)
-Hemorrhagic foci on MRI performed in the early post-biopsy period (11)
-PI-RADS 4–5 lesions that had no visible contact with capsule (15)
-Lesions that could not be verified by pathological mapping (13)
Images were obtained using a 1.5T MRI scanner (General Electric Optima 450W, 1.5T, GE Medical Healthcare, USA). A 16-channel body coil was used. While performing perfusion imaging, agadobutrol-based contrast agent (Gadovist®, BAYER) was administered intravenously at a dose of 0.1 mmol/kg(Table 1). The demographic characteristics of the cases, their PI-RADS scores, and the TCL of the lesions were recorded. Moreover, the LL and the presence of EPE were recorded separately, both radiologically and pathologically. The MR images were evaluated by two independent observers who had 4 and 3 years’ experience in prostate mpMRI. The assessments were made with the observers blinded to the pathology results.
First, observers assessed the MR images of 130 patients independently and categorized them according to PI-RADS v2.1 In cases where there was suspicion of multifocal PCa, only the index lesion, which is consideredthe largest among the lesions having the highest PI-RADS score, was evaluated. An assessment was made regarding the radiological presence of EPE. Afterward, the LL and the TCL were measured. LL was measured on theplane where the lesion had the longest axis. However,TCL was digitally measured on the T2W images for which contact with the capsule was the most visible (Figure 1). Moreover, the lesions that were not in contact with the capsule were recorded in a separate group. In this group of lesions, the distance between the lesion and capsule was measured, and the histopathological presence or absence of EPE was recorded.
Radiological EPE was assessed by considering the criteria previously described in the literature. Criteria that suggest radiologic investigation for EPE are (1) capsular irregularity, (2) bulging in the capsule, (3) capsular retraction, (4) rectoprostatic angle obliteration, (5) extracapsular tumor, (6) extracapsular tumor enhancement, (7) asymmetry or direct involvement in neurovascular bundles, (8) asymmetric enhancement of the neurovascular bundles, and (9) pathological signal change in seminal vesicles. The relation between the lesion and the capsule was assessed using T1 weighted (T1W) dynamic, diffusion weighted (DW), apparent diffusion coefficient(ADC), and T2W images. After radiological evaluations, histopathological data were evaluated in terms of LL, Gleason score, and the presence of EPE. The data were also classified according to the International Society of Urological Pathology (ISUP) grade groups, along with the Gleason score. In addition to these evaluations, mapping was performed for all cases to confirm the lesion detected radiologically. This was done to assess the interobserver agreement in terms of radiological findings and to compare them with histopathological data. During the statistical analysis, categorical data were expressed as values and percentages. The numerical data were expressed as mean, standard deviation, minimum, and maximum values. The Chi-square test was used to compare the categorical data, and the independent-sample t-test was used to assess the difference between the mean values of the parametric data distributed between groups. Furthermore, the Mann-Whitney U test was used for nonparametric data. In cases with significant differences between the groups, the optimum cut-off point was calculated by performing ROC analysis, and area under curve, sensitivity, and specificity values were calculated. Spearman correlation analysis was conducted to evaluatecorrelations between nonparametric numerical data. In the assessment of the interobserver agreement, weighted Kappa for PI-RADS, Cohen’s kappa for binomial categorical variables, and intraclass correlation coefficient for numerical data were calculated. SPSS 21.0 (IBM Corp., New York, USA) was used in statistical analyses. Cases where p<0.05 were considered to be statistically significant.