Magnetic resonance imaging in staging of locoregional prostate cancer : comparison of results with analysis post-surgical histopathology

Conventional staging for locoregional prostate adenocarcinoma has been demonstrated as potentially underdiagnosing. Therefore, prostate MRI is emerging as an important tool for staging before surgery. Advanced techniques such as diffusion and dynamic contrast enhancement also contribute to increasing its accuracy. In this preliminary study, MRI was compared with prostate histopathology samples, reaching 78% sensitivity and 100% specificity for tumor localization; 33% sensitivity and 100% specificity for extracapsular extension; 100% sensitivity and 100% specificity for involvement of the seminal vesicles. It is possible to believe that these preliminary results are promising, and more cases will tend to confirm these data.


INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION
P hysicians often face histopathology results of radical prostatectomy specimens in patients with advanced malignancy thaT were expected to have a prostate-confined disease.The traditional locoregional staging with digital exam, transrretal ultrasonography and computed tomography is notoriously limited 1,2 and the use Magnetic Resonance Imaging (MRI) has emerged as the image category of choice.Its advanced techniques such as diffusion, dynamic contrast and spectroscopy have added specificity to the findings of basic sequences 3,4 .
The aim of this study is to compare MRI findings suspicious for prostate cancer with histopathological examinationS in patients undergoing radical prostatectomy considereing tumor location (unilateral or bilateral), extra-capsular extension, seminal vesicle invasion and obturator lymph node invasion.

METHODS METHODS METHODS METHODS
Between March and June 2009 we evaluated 11 consecutive patients in the HUCFF-UFRJ diagnosed with prostate cancer, with an indication for radical prostatectomy according to the criteria of the Brazilian Society of Urology guidelines.The study was approved by the HUCFF Ethics in Research Committee and logged in to SISNEP with CAAE number 0057.0.197.000-09.All patients signed an informed consent.We performed MRI of the prostate with a 1.5T apparatus (Avanto, Siemens, Germany).The suspicious appearance for neoplastic involvement comprises nodular areas with low signal on T2-weighted sequences (Figure 1).We also obtained advanced diffusion and dynamic contrast enhancement sequences to confirm and increase the specificity of T2-weighted sequences, according to widely known criteria 3,4 (Figures 2 and 3).Extra-capsular extension was considered when we found extra-prostatic nodules, obliteration of periprostatic fat, invasion of the neurovascular bundle or evident trans-capsular tumor 4 .Surgical specimens were sent to standard histopathologic examination.The results were compared using the following criteria: location (unilateral or bilateral), extracapsular extension, seminal vesicle invasion and obturator lymph node invasion.

RESULTS RESULTS
In all 11 cases the main tumor focus (>0.5 cm) was correctly located by MRI.As for tumor location (unila-teral x bilateral), MRI showed a sensitivity of 78% and specificity of 100%, with an accuracy of 82%.The lowest sensitivity was due to microscopic foci (<0.5 cm) of bilateral disease, undetectable by MRI.In search of extracapsular   Anticipating the results of histopathology, thus optimizing neoplasia staging, is a big challenge in radiology.Although we are dealing with a method dependent on experience and training of the radiologist and ours is a small sample, initial results are promising.The use of magnetic resonance imaging in preoperative staging of prostate adenocarcinoma attempts to predict events that may influence surgical approach and the patient's postoperative staging 5 .More cases to be aggregated in this study can generate analyses with a higher degree of statistical significance.

Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 -
Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 -Map of apparent diffusion coefficient showing hypointense area in the same location that the image weighed in T2, suggesting high cellularity (arrow).

Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 -
Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 -T2-weighted image showing hypointense nodular area in the prostate peripheral zone in the middle third to the right (arrow).