The American Urological Association (AUA), in collaboration with the Society of Abdominal Radiology (SAR), convened for a Prostate Cancer Disease Focused Panel to conduct a literature review and create consensus statements regarding the role of prostate magnetic resonance imaging (MRI) and MRI-targeted biopsy in patients with a prior negative biopsy. This came as a result of recent improvements in technology and the increasing number of urological practices incorporating prostate MRI into the routine care of select patients with a prior negative biopsy.
There are currently 3 main strategies for targeted MRI in a repeat biopsy: cognitive targeting, performing a biopsy while the patient is in an MRI gantry, and real-time MRI/ultrasound fusionguided prostate biopsy. While many studies demonstrate the usefulness of each procedure, no studies have compared these methods, according to the consensus statement.
Cognitive targeting requires the least technology; it involves estimating the location of the tumor detected on the MRI and transferring the target to a transrectal ultrasound without additional technological guidance. The lack of visual feedback, according to the consensus statement, results in a less accurate and reliable approach, since it largely relies on the expertise of the practitioner. The statement does recognize, however, that cognitive biopsy procedures have shown positive results in the literature the AUA and SAR reviewed.
The second technique, performing a biopsy while the patient is in an MRI gantry, offers the advantage of being the most direct targeting for a repeat biopsy. With this technique, MRI images are taken to confirm placement of the biopsy needle in the target tumor. However, the consensus statement points out that this method is more time-consuming and labor-intensive, and may be uncomfortable for the patient, who must lie in a prone position throughout the procedure.
The real-time MRI/ultrasound fusion-guided prostate biopsy involves a planning session before the procedure, in order to define the boundaries of the prostate and the location of the targeted tumor(s) through an MRI scan. The prostate and target map is then loaded into the fusion biopsy system, and at the time of the biopsy, the MRI data are combined with the transrectal ultrasound, effectively linking the movements of the 2 imaging results so the biopsy is performed under transrectal ultrasound, but using MRI guidance. The consensus statement lauds this approach for its familiar procedures and its relatively shorter duration to perform, but recognizes the possibility of a co-registration error impeding the accuracy of the results.
While the use of advanced technology such as a fusion system or an in-bore biopsy system may be helpful, the superiority of any specific approach has not been established, according to the statement. One approach may be to apply different methods of MRI targeting depending on the characteristics of the tumor. For example, a urologist may use an in-bore or fusion system for tumors that are smaller in length or in a region difficult to access (such as the anterior or apical prostate) while limiting cognitive targeting to other targeted tumors.
Although fusion and in-bore biopsy systems may have value in improving biopsy yield, they have high costs associated with them, according to the guidelines. The consensus statement supports cognitive targeting as a sound approach for the detection of prostate cancer when advanced technologies are not available, and when operators are skilled with imageguided procedures.
The consensus statement advises that practitioners should take at least 2 cores from each MRI-targeted tumor biopsy procedure. It also advises that systematic and MRI-targeted cores be separately labeled, given that currently accepted clinical nomograms are derived from data based on standard systematic biopsy results.
After an initial negative biopsy, there has been an ongoing need to improve strategies for performing repeat biopsies. There is an additional need to improve the diagnostic yield from repeat biopsies, in order to prevent patients from undergoing unnecessary repeat biopsy procedures. While there are options for patients with a prior negative biopsy, if a subsequent biopsy is recommended, using MRI-targeted cores improves the detection of clinically significant disease over a standardized repeat biopsy.
However, several challenges exist in optimally using and assuring quality of prostate MRI scans. There is variation in image quality as well as in the interpretations of radiologists examining the images. There is currently no standardization for image quality, and so even when different centers are using the same equipment, there may not be the same examination quality, leading to false-positive or falsenegative readings.