Abbreviations:PSA: Prostate Specific Antigen; US: Ultra Sonography; ACC: American College of Radiology; ESUR: European Society of Urogenital Radiology; PI-RADS: Prostate ImagingReporting and Data System
Prostate cancer is the second most prevalent cause of cancer death of men in Western Europe and in the United States . For patients with high clinical suspicion for prostate cancer (abnormal digital rectal examination and/or elevated prostate-specific antigen (PSA) level, the standard diagnostic tool for the diagnosis is the systematic trans rectal ultrasonography (US)-guided 10 to 12 core biopsy [1-4]. Multiparametric prostate magnetic resonance (MR) imaging by applying T2-weighted imaging, diffusion-weighted imaging (DWI), and dynamic contrast-enhanced imaging (DCI) has been proven to improve the early detection, and localization of prostate cancer [1-5].
Over the past 10 years, the use of multiparametric MRI as a tool for biopsy targeting of suspicious lesions for prostate cancer revealed significantly higher cancer detection rates. Overall, there exist a variety of methods, such as cognitive fusion, MRI-Ultrasound (US) fusion and direct in-bore MR-guided biopsy which can be compared with standard template-based the Prostate Imaging Reporting and Data System (PI-RADS), an expert consensus document has been introduced by the European Society of Urogenital Radiology (ESUR) and the American College of Radiology (ACC) as a standardized lexicon and diagnostic instrument for interpretation of multiparametric prostate MR images . This stratified the malignant capability of individual lesions that could be detected on MR images. PI-RADS version 2, the improved system of the first version was updated and published in 2104. With PI_RADS version 2, the evaluation of DCE imaging was simplified and the criteria for category 3 lesions were elucidated [1,7,8]. In a multicenter, paired-cohort, confirmatory study .
Hashim U Ahmed could show, that the use of multi-parametric MRI for patients with a suspicion of prostate cancer might allow 27% of patients avoid a primary biopsy and allow to detect 5% fewer clinically insignificant cancers. Compared with the standard TRUS biopsy 18% percent more cases of clinically significant cancer might be detected. Moreover, MRI as a triage test before first prostate biopsy could reduce unnecessary biopsies by a quarter . Multiparametric MRI and MRI-guided biopsy techniques thoughbear the risk to overlook or misscancers, especially cancers with small volumes (<0.5ml, and low grade, Gleason score ≤6) [4,5,9]. In a study of De Visschere the negative predictive value for the detection rate of high-grade cancers (tumor volume <0.5ml, Gleason score ≥7) was 95, 4% [3-5,9]. When stratifying multiparametric MRI and in-bore MRI-guided prostate biopsies according to PI-RADS 2 the system could identify 95% of prostate cancer foci ≥0.5ml, but this was limited to the assessment of tumors with a Gleason score, GS≥4+3=7 [1,5,10]. One study with a critical look at PI-RADS System, version2 summarized that a wide range of questions remains to be answered regarding how to apply the system in directing patient management . For instance, which overall PI-RADS assessment categories are targeted bya reasonable biopsy? In lesions with PI-RADS 3, which are declared as intermediate “the presence of clinically significant cancer is equivocal”  the system recommends clinical follow-up. However, should we not in contrast to that debate applying a targeted biopsy for patients with rising PSA and a PI_RADS 3 lesion?
In our institute we evaluated the impact of PI-RADS 3 score in differentiating these equivocal lesions as benign or malignant for 54 men with elevated PSA levels (PSA>4ng/ml) and abnormal multiparametric MRI. For patients with PI-RADS score 4 and 5 we ruled out the sensitivity and the positive predictive value of MRI-guided prostate biopsy in determining positive histological tumor results. 34 men were biopsy naive, 20 patients had prior tumor negative biopsies. The in-bore MRI-guided prostate biopsies were performed in a standard 1.5 Tesla scanner. A mean
of 2.2 cores was taken from each tumor suspected lesion. The PIRADS
scores of the tumor suspected areas were compared with
the histological findings of the biopsy. By applying the PI-RADS
system 54% of cancers were detected by MRI-guided biopsy with
a rate of 90% of significant tumors. In 25 cases of PI-RADS score
3 no cancerous tissue was found in the histology report. In one
man a high grade prostatic intraepithelial neoplasia (PIN) was
detected. The sensitivity of PI-RADS scores 4 and 5 was 90%, by
a positive predictive value of 70%.
Based on our population we could assess a highly sensitivity
and a fair positive predictive value in detecting significant
prostate cancers by stratifying the MRI-guided biopsy with the
PI-RADS system. For patients with PI-RADS 3 lesions a patient
management is necessary in order to differentiate candidates
fitting for a clinical follow up or suitable for a targeting biopsy.
PI-RADS 3 score could not be confirmed as an absolute marker in
patient clinical management care. In our study PI-RADS 3 lesions
revealed only benign conditions.