Accuracy of multiparametric MRI targeted 3D fusion prostate biopsy in naive patients
Compared to TRUS, which is the conventional imaging used to guide PB, magnetic resonance imaging (MRI) offers the attractive potential to improve sensitivity, through a refined imaging of anatomical structures and landmark and providing information on metabolic activity of areas suspicious for cancer [1-7]. Major drawbacks of MRI are costs, time-consume and the limited reproducibility in most settings. Although biopsy can be performed under TRUS guide and targeted basing on MRI findings, the best option is fusing the stored MRI with the real-time TRUS images, thus combining the high imaging resolution of MRI with the ease and reproducibility of TRUS [1-7]. We assessed sensibility, specificity, positive predictive value (PPV) and negative predict value (NPV) of multi-parametric magnetic resonance imaging 3D targeted fusion prostate biopsy in naive patients.
Methods and results
A series of 68 consecutive patients were submitted to multi-parametric magnetic resonance imaging (mMRI) 3D targeted fusion prostate biopsy in two centers by two surgeons, after a learning curve of about 100 procedures, during 2013. Every patient read and signed a dedicated informed consent. None of the patients was previously biopsied. All of them underwent mMRI 1 to 3 weeks before biopsy. Areas on mMRI were considered pathologic according to PIRAD score. At least one pathologic area (target) on mMRI, defined by a PIRAD score ranging from 3 to 5, was found in 49 (72%) patients whereas the remaining cases were negative (28%). Mean age of the population was 63 years. Estimated prostate volume was less than 60 mL in 90% of cases. PSA was 20 in 3. Digital rectal examination was always un informative. All the patients were submitted to a cleansing enema before the procedure. Moreover a fluorochilonic therapy was began 2 days before and discontinued 5 days after the biopsy. All the procedures were performed by means of the Koelis Urostation which allows for real time 3D fusion of the mMRI and transrectal ultrasound imaging. Other main characteristics of the Urostation were the ability to record the trace of every puncture of prostate and to simulate the trace of a biopsy before performing it actually (virtual biopsy). Local anesthesia was performed by injection of lidocain 2% solution along the periprostatic tissue from the base to the apex. Every single biopsy performed was labeled, according to the number assigned by the Urostation, and put in a box. A total of 20 cores were obtained for each session of which, at least 2, from each target. A per person analysis was performed to assess sensibility, specificity, PPV and NPV of procedure.
Overall, prostate cancer (PC) was detected in 32 patients out 68 (47%). PC was found in 29/49 (59%) patients (20 in the target 9 outside the target) with at least one target (Gleason score sum was 6 in 4 cases and 7 or more in the remaining 16) and in 3 (13%) patients without any target (Gleason score sum was 6 in 2 cases and 7 or more in 1 case). Thus, the per person analysis revealed that the identification of a target by means of mRI puts at an incresed risk of PC detection a subject with a relative risk of about 3.748 (95%CI, 1.376 – 14.733). Respectively sensitivity was 0.906 (95%CI 0.78 – 0.974), specificity 0.444 (95% CI 0.332 – 0.505), PPV 0.592 (0.509 – 0.636) and NPV 0.842 (0.63 – 0.9579). Particularly among all patients mMRI and targeted biopsy correctly identified 36/68 (52%) patients. Interestingly, including the 7 patients with a positive biopsy outside the target but omolateral to the target the proportion reaches 43/68 (63%). Both the ratios are significantly above rates recently obtained from a systematic review of all papers regarding mMRI targeted biopsy, which shows an overall 30% detection rate  Finally, the complication rate was acceptable. Acute urinary retention and urosepsis occurred respectively in 2 (1.6%) and 3 cases (2.4%).
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