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.