Multiparametric magnetic resonance imaging (mpMRI) has become a major tool for prostate cancer (PCa) diagnosis and treatment decisions, and can help in identifying significant PCa and in guiding targeted biopsies  and . Moreover, given the fear of PCa overtreatment, the role of prostate biopsies has evolved during the last decade from purely cancer detection to investigating how biopsy results can assist in clinical management of patients. Systematic biopsies may involve an excessive price in answering remaining questions regarding PCa.
Is mpMRI the ideal tool for providing insight into these remaining questions? Evidence suggests that mpMRI clearly improves patient management. If patients have normal mpMRI results and negative biopsies, we can avoid further unnecessary tests  and .
Can we exclude significant PCa in cases of normal mpMRI? In a recent meta-analysis, the negative predictive value of mpMRI for exclusion of significant disease ranged from 63% to 98%. This means that mpMRI can miss one third of significant PCas that would have been detected by systematic biopsies. Thus, mpMRI is not sufficient to definitively rule out significant disease. High interobserver variability and low diagnostic peformance for low-volume lesions may play a role in this limitation  and . Is abnormal prostate mpMRI always synonymous with PCa? False positives are frequent, but mpMRI defenders could point to inaccurate sampling for random biopsies.
Despite these considerations and regardless of whether mpMRI will gain acceptance and replace random biopsies in the near future, physicians should be aware that all treatment-decision making and monitoring processes will be subject to significant change. All the inclusion criteria for active surveillance protocols, all the criteria for reclassification and deferred treatment, and all well-established prediction tools are based on assessment via systematic biopsies. These evidence-based criteria are derived from long-term prospective trials and large retrospective studies. Tracking a small PCa focus of Gleason score 7 by mpMRI could surely improve our initial risk assessment. Nevertheless, such evolution will greatly change the current PCa management paradigm. If an mpMRI-guided core has a small focus of grade 4 disease not detected by systematic biopsies, should we propose radical treatment? Recall that the presence of grade 4 disease is not a contraindication to active surveillance . If mpMRI shows small lesions without diffusion restriction, should we avoid biopsies and promote repeat mpMRI to monitor progression? It should be remembered that Gleason 6 disease can drive metastatic spread and that both radiological significance and radiological progression are not yet clearly defined . Are detailed biopsy parameters useless compared with mpMRI findings? We should not forget that the tumor burden detected in systematic biopsies (number of positive cores, percentage core involvement) is a strong predictor of adverse pathology and oncologic outcomes and should still influence treatment choice .
We should keep in mind that the road to achieving a standardized protocol for an ideal systematic biopsy protocol was long, and included a new Gleason grading system, extended schemes, far lateral sampling, and improvements in immunohistochemistry-based pathologic assessment. mpMRI will certainly change our biopsy decision-making process and our way of performing biopsies, with the aim of decreasing the rate of unnecessary and improving PCa risk assessment. mpMRI is already (or will be in the very near future) a mandatory tool in low-risk and intermediate-risk PCa for monitoring and treatment (active surveillance, focal therapy). However, continued improvements in standardization of technical parameters, functional sequences, cost evaluations, and image reporting systems, in addition to well-designed comparative trials, are critically required before mpMRI can reach its full potential.
Conflicts of interest
The authors have nothing to disclose.
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a Saint-Jean Languedoc Hospital, Toulouse, France
b Department of Urology, Centre Hospitalier Universitaire Mondor, Créteil, France
Corresponding author. Department of Urology, Centre Hospitalier Universitaire Mondor, 51 Avenue du Mal de Lattre de Tassigny, Créteil 94000, France. Tel. +33 1 49812554; Fax: +33 1 49812552.
© 2015 European Association of Urology, Published by Elsevier B.V.