Patient’s demographic data
Approval from our institution’s ethics committee was acquired, and informed consents were acquired from all patients before inclusion in this work. This prospective study included 60 male patients with clinically suspected prostate cancer; their age ranged from 48 to 82 years, and the mean age ± SD was 65 ± 8 years. Patients did not receive chemotherapy, radiotherapy, or hormonal therapy prior to the MRI examinations. No biopsies were performed to all patients prior to the MRI examinations.
Inclusion criteria
Patients with clinically suspected prostate cancer by digital rectal examination or by high serum PSA (> 4 ng/dl) were included.
Exclusion criteria
Patients who had contraindications to do MRI as patients with cardiac pace maker, with cochlear implant, and ocular foreign body; patients who refused contrast media injection; patients who had contraindications for contrast media injection as patients with impaired renal function; patients with poor quality of the MR images as patients with motion artifact; and patients who were lost and their pathological results were not available were excluded.
MRI technique
The procedure was conducted using a 3-T MRI scanner (Ingenia, Philips medical systems, Veenpluis, Netherlands). Patients lied in the supine position, and an abdominal eight-channel surface phased array coil was well fitted on the pelvis. The region of interest was taken from the urinary bladder to the end of the prostate. The following sequences were obtained for all patients: (1) T2-weighted images (field of view (FOV): 200 mm, repetition time (TR): 5000 msec, echo time (TE): 110 msec, slice thickness: 3 mm, no interslice gap, and matrix: 288 × 192). According to the recommendations of the PI-RADS version 2.1, T2W images were acquired in axial (straight axial), sagittal, and coronal planes. (2) Diffusion-weighted images (DWI) (FOV: 350 mm, TR: 7255 msec, TE: 85 msec, slice thickness: 3 mm, no interslice gap and matrix: 128 × 96). Regarding the b values, we used low (0 s/mm2), intermediate (800 s/mm2), and high (1400 s/mm2) b values. ADC maps were obtained from DW images at b0 and b1400 s/mm2 gradients. (3) Dynamic contrast enhancement (DCE) (FOV: 200 mm, TR: 19 msec, TE: 1.93 msec, slice thickness: 4 mm, no interslice gap, temporal resolution < 15 s and matrix: 320 × 192). DCE images were obtained after IV injection of contrast media (Dotarem (Gadoteric acid)) at a dose of 0.1 mmol/kg (maximum dose 15 mmol) at a rate of 3 mL/s. A contrast injection was performed using an automatic injector.
Image interpretation
Biparametric and multiparametric MR images were analyzed on the basis of the PI-RADS version 2.1 by 2 radiologists (EA, ME) with 5 and 14 years’ experience in uroradiology. The two radiologists analyzed the biparametric MR images at first (T2WI, DWI, and ADC), and then, subsequently on the same setting, the multiparametric MR images were analyzed. The two radiologists were blinded to the results of histopathological examination. On the basis of the PI-RADS version 2.1 all detected lesions were assigned a score from 1 to 5 representing the probability of clinically significant PCa (PI-RADS 1: very low, PI-RADS 2: low, PI-RADS 3: intermediate, PI-RADS 4: high, PI-RADS 5: very high). For the transitional zone (TZ) lesions, the scoring was done mainly on T2WI. Category 2 lesions on T2WI were raised to category 3 when the lesions were categorized as 4 or 5 on DWI. Category 3 lesions on T2WI were raised to category 4 when they were categorized as 5 on DWI. For peripheral zone (PZ) lesions, the scoring was done mainly on DWI. Category 3 lesions on DWI were raised to category 4 when they showed positive enhancement on DCE on mpMRI. On bpMRI, the categorization of PZ lesion was done only on the basis of DWI and the lesions on category 3 will remain in category 3 and not upgraded. In cases with multifocal lesions, we reported only the index lesion for statistical analysis. On basis of PI-RADS version2.1, the index lesion is defined as the lesion that shows the highest PI-RADS assessment category, and if the highest PI-RADS Assessment Category is specified to more than or equal two lesions, the index lesion is the lesion that revealed extraprostatic extension (EPE). If EPE was not present in any of the detected lesions, the index lesion will be the lesion that showed the largest dimensions and the highest PI-RADS Assessment Category. The two radiologists joined and reached a correspondence about the bpMRI and mpMRI scores for controversial cases.
Final diagnosis
TRUS-guided biopsy (standard 12-core random systematic biopsy) was performed for all patients after the MRI studies. The duration between the MRI study and the histopathological examination was 7–10 days. TRUS-guided biopsy was done by using (Flex focus 500, bk medical, Herlev, Denmark) with high-frequency transrectal transducer (5–9 MHz) with a condom cover. The patient lied in a lithotomy position. A lubricant gel is used with lignocaine cream before insertion of the probe. Axial and coronal scans were obtained to demonstrate the volume of the prostate, any abnormal foci at the peripheral zone, and the infiltration of the seminal vesicles by malignancies. Twelve cores were taken, and tissue biopsies were sent for histopathologic evaluation.
When TRUS-guided biopsy revealed PCa, open prostatectomy was performed and the diagnosis of prostatic carcinoma was confirmed. According to PI-RADS v2.1, csPCa is diagnosed by histopathology as the lesion with Gleason score more than 7 (including 3 + 4 with prominent but not predominant Gleason 4 component), and/or volume more than 0.5cc, and/or EPE. In order to match the MRI findings with the results of the prostatectomy specimen, we reported the site of the index lesion on MRI according to the sector map proposed by the PI-RADS version 2.1, and subsequently, we obtained the prostatectomy results for the related zones.
Statistical analysis and data interpretation
Data were fed to the computer and analyzed using IBM SPSS Corp. (released in 2013, IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp). Qualitative data were described using numbers and percentages. The significance of the obtained results was judged at the (0.05) level. Diagnostic accuracy for categorical variables was detected by cross-tabulation to detect true positive and true negative, and then a calculation of sensitivity, specificity, positive predictive rate, negative predictive rate, and accuracy. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of both bpMRI and mpMRI of PI-RADS version 2.1 were calculated two times, one time when considering PI-RADS categories 4 and 5 as malignant lesions and the other time when considering PI-RADS categories 3, 4, and 5 as malignant lesions.