Multiparametric magnetic resonance imaging-targeted biopsies in the detection of clinically significant prostate cancer

SUMMARY

Unlike other solid malignancies where a biopsy targets a visible lesion, in prostate cancer the most common technique is a 12-core systematic biopsy of the prostate not targeting a specific lesion. This method leads to overdiagnosis and overtreatment and cannot avoid pitfalls such as grade misclassification. Multiparametric magnetic resonance imaging (mpMRI) allows the performance of targeted biopsies ande questions regarding the best biopsy protocol remain.

Ahdoot et al.[1] recently published their study evaluating the use of MRI-targeted, systematic, or combined prostate biopsy in prostate cancer (PCa). The study included 2103 men with a clinical suspicion of PCa and visible lesions on the mpMRI. All patients underwent a combination of 12-core systematic biopsy and mpMRI-targeted biopsies. PCa was diagnosed in 1312 patients (62.4%) using both methods. Cancer detection rates on mpMRI-targeted biopsy alone were lower compared with those of systematic biopsy for Grade group 1 but higher for Grade groups 3–5 The combination was superior as it led to cancer diagnosis in 208 more men (9.9%) than either method alone and in upgrading to a higher Grade group on 458 men (21.8%). If only mpMRI-targeted biopsies are performed, 8.8% of clinically significant PCa patients would have been misclassified in terms of grade. In addition, in men who underwent subsequent radical prostatectomy after PCa diagnosis, the combination was associated with the fewest upgrades to Grade group 3 or higher on histopathological analysis of surgical specimens (3.5%), as compared with mpMRI-targeted biopsy (8.7%) and systematic biopsy (16.8%) alone.[1]

COMMENTS

A head-to-head comparison of systematic biopsy versus mpMRI-targeted biopsy was performed by van der Leest et al.[2] in biopsy-naïve men with a clinical suspicion of PCa. Using the mpMRI pathway leads to identical rates of detection of clinically significant PCa as systematic biopsies but reduced diagnosis of clinically insignificant cases. If systematic biopsy is not performed along with mpMRI-targeted biopsy, 4% of clinically significant PCa s would be missed.[2] The value of combining systematic biopsy with mpMRI-targeted biopsy was also evaluated by a Cochrane meta-analysis[3] and MRI-FIRST trial.[4] Adding mpMRI-targeted biopsies to systemic biopsy protocol leads to higher detection rates of clinically significant PCa, which may be as high as 20% and 30% for Grade group ≥2 and Grade group ≥3, respectively, in biopsy-naïve men. The profit is even greater in cases of repeat biopsy where the combination increases the detection of Grade group ≥2 by approximately 40%. On the other hand, if systematic biopsy is not performed along with mpMRI-targeted biopsies in biopsy-naïve men, we would miss about 16% of ISUP Grade ≥2 PCa and 18% of ISUP grade ≥3 PCa cases.[3,4]

In conclusion, the study published by Ahdoot et al.[1] supports the role of combining mpMRI-targeted biopsies with systematic prostate biopsy in biopsy-naïve men with a clinical suspicion of PCa. The major strength of this study is that it includes both biopsy-naïve men and patients with a previous negative biopsy. The investigators had a high level of experience in mpMRI reading as is evidenced by the small percentage of PIRADS 3 diagnosed (6%–12%). However, these results may not be reproducible in other centers with less experience. Another weakness of the study is that mpMRI-targeted biopsies were performed before systematic biopsy and as a result, the operator performing systematic biopsy may be influenced by marks in the prostate made by the previous targeted biopsy.