In this study, there was no significant difference between the CDR in the combination of 14-core SBs and the CDR using 10-core SBs. Based on this result, our facility has now reduced the number of biopsy cores in SB to 10 and conduct MRI–TRUS fusion biopsy. Further, the combination of SB and MRF–TB had the highest CDR in our study. This result was consistent with those of other reports. Likewise, Calio et al. found that combining SB with MRF–TB significantly reduced surgical GS upgrading compared to SB alone[9]. Additionally, patients with a PI–RADS score of 3 have a low CDR, but a certain number of PCa cases with high GS do exist, necessitating proper precaution. Therefore, in patients with MRI lesions having a PI–RADS score of 3 or higher, we should consider prostate biopsy under MRF–TB.
In recent years, many studies have shown the effectiveness of MRF–TB. It was demonstrated that the csPCa detection rate of men undergoing MRF–TB was higher than that of men undergoing TRUS biopsy [10]. Siddiqui et al. reported that in the prospective single-group cohort of 1,003 men, the number of high-risk cancers detected increased and the number of low-risk cancers detected decreased with the use of MRF–TB[11]. Baco et al. reported comparable detection rates of csPCa between the 2-core MRF-TB and the 12-core SB [12]. Ukimura et al. reported that the TRUS visibility of an MR-suspicious lesion facilitates image-guided biopsies, resulting in higher detection of csPCa [13]. Based on these recent studies, MRF–TB has the potential to be a gold standard diagnostic tool for men suspected of PCa. In addition, MRF–TB has made it possible to determine the GS and cancer localization of csPCa with high accuracy, making it easier to track the cancer progression of individual patients. The detailed information obtained by MRF–TB is expected to be applied to the accurate adaptation of active surveillance, surgical resection with improved curability, and nerve preservation, with further application in focal therapy. TRINITYTM records the 3D position information of the tissue collected by the biopsy and enables 3D display, making it easier to visualize where the cancer tissue is in the prostate. At our institution, in cases where robot-assisted laparoscopic radical prostatectomy (RALP) is to be performed after MRF–TB, it is used to evaluate the localization of cancer in nerve-preserving surgical selection. Moreover, we tried to visually improve the surgical precision by displaying a 3D model on the da Vinci Surgical SystemTM during RALP.
Prostate biopsy is essential for the diagnosis, risk stratification, and treatment planning in PCa. However, the overdiagnosis and overtreatment of cisPCa pose serious clinical and economic problems. For instance, the medical costs associated with prostate biopsy include the costs of testing and radical treatment for cisPCa, and the associated medical costs of erectile dysfunction and dysuria are mainly attributed to treatment. MRF–TB has the potential to resolve these problems. MRF–TB can detect csPCa with a lower number of biopsy cores. A lower number of biopsy cores not only reduces patient discomfort but also minimizes the risk of complications associated with treatment, such as infection. As Onik et al. reported that the localization of csPCa can be diagnosed using mpMRI with a 3-mm slice thickness, it is expected that the use of mpMRI is efficient [14]. If there is no obvious lesion noted on mpMRI, clinical follow-up without prostate biopsy can reduce the problem of overdiagnosis and overtreatment [15]. mpMRI improves the cost-effectiveness of prostate biopsy; however, it should be noted that false negatives can occur in about 20% of cases [16, 17]. Other reports suggested that only 17.4% of cribriform tumors in pure form were visible on MRI [18]. Therefore, in the current imaging diagnostic technology, it is possible that merely performing MRF–TB on MRI lesions may overlook csPCa. Thus, the combined use of SB is considered essential. In fact, it is said that the false-negative rates of csPCa for targeted fusion prostate biopsy were 16.2% and 39.7% for patients with a PI–RADS score of 3 or greater and those with a PI–RADS score of 4 or greater, respectively [19].
Although the effectiveness of MRF–TB has been reported previously, there is a report stating that there is a learning curve in establishing the procedure. Meng et al. reported that the csPCa detection rate increased by 26% (50 to 76%, p=0.025) with time in men with a PI–RADS 4/5 ROI. It is necessary to acquire a certain number of cases in order to achieve stability in performing the procedure. Furthermore, there is no clear standard for the number of MRF–TB cores to be collected for each MRI lesion. The number of TB cores is determined based on the judgment of the examiner according to the size and location of the MRI lesion. According to Porpiglia et al., taking two cores at the center of the index lesion regardless of the diameter may provide more accurate cancer detection and optimize the chances of finding the highest Gleason pattern [20]. On the other hand, there are opinions skeptical of the use of 2-core TB, and Dimitroulis et al. reported that the diagnostic utility does not change despite the use of one or two cores for the target lesion [21].
This study confirmed the effectiveness of MRF–TB; however, there are some limitations. First, not all patients undergoing MRF–TB were diagnosed with PCa in this study. Furthermore, since not all patients diagnosed with PCa selected to undergo curative prostatectomy, comparison between the biopsy specimen and the whole prostate specimen was incomplete. For these reasons, it was not possible to reliably measure the standard parameters such as actual sensitivity, specificity, diagnostic accuracy, etc. This aspect is considered a major limitation of studies focusing on MRF–TB. Second, improvements in the PI–RADSTM and the collaboration among radiologists, pathologists, and urologists are important factors that have been previously shown to contribute to the enhancement of cancer detection over time. However, it is difficult to quantify these factors [22, 23]. Third, in this study, the comparison is based on the assumption that the number of biopsy cores has been reduced. Therefore, we did not compare actual biopsy results. Forth, when an examiner is performing SB, he/she already has prior knowledge of suspicious lesions based on either US images or fusion MR images. Therefore, there was a possibility that bias occurred during random sampling.
Despite the limitations, our study has several strengths. First, at our facility, for all male patients who presented with a high PSA value, the possibility of selective bias can be reduced to a certain extent because we performed MRI prior to biopsy when medically possible. Furthermore, since the prostate biopsy was performed by a single examiner, we believe that stability of the procedure can be achieved.