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28-11-2018 | Prostate cancer | News

Multiparametric MRI does not render systematic prostate biopsy obsolete

medwireNews: Pre-biopsy multiparametric magnetic resonance imaging (MRI) improves the detection of clinically significant prostate cancer in biopsy-naive patients but does not appear to remove the need for systematic biopsy, MRI-FIRST study data show.

Indeed, the proportion of patients with clinically significant prostate cancer of International Society of Urological Pathology grade group 2 or higher (csPCa-A) detected among 251 with stage T2c or lower prostate cancer was 29.9% with systematic biopsy and 32.3% with targeted biopsy based on multiparametric MRI findings, a nonsignificant difference.

However, Olivier Rouvière (Hôpital Edouard Herriot, Lyon, France) and co-investigators note that csPCa-A would have been missed in 5.2% of patients if systematic biopsy had not been done, and in 7.6% of patients if targeted biopsy had not been done.

“This finding suggests that detection of such tumours is improved when systematic biopsy and targeted biopsy are combined,” they write in The Lancet Oncology.

For the study, all participants underwent multiparametric MRI and systematic biopsy (mean 12.2 cores per patient). Those with positive multiparametric MRI (Likert score ≥3; n=198) also underwent targeted biopsy of up to two lesions (three cores per lesion).

Overall, there were 94 (37.5%) cases of csPCa-A detected among the 251 patients.

Of these, 13 (13.8%) cases were detected by systematic biopsy only, 19 (20.2%) by targeted biopsy only, with the remaining 62 (66.0%) cases detected by both techniques.

Similar results were observed when using the wider csPCa-B definition of clinically significant prostate cancer, which also includes grade group 1 tumours with a maximum cancer core length of 6 mm or longer, but detection of the most aggressive tumors (grade group 3 or higher; csPCa-C) was significantly lower with systematic biopsy than with targeted biopsy.

By contrast the detection of non-clinically significant prostate cancer was significantly higher with systematic biopsy than with targeted biopsy.

“Thus, using multiparametric MRI as a triage test (no biopsy when multiparametric MRI is negative, targeted biopsy only when multiparametric MRI is positive) might be a valid approach, but only for diagnosing highly aggressive tumours,” Rouvière et al remark.

In an accompanying comment, Rajiv Jayadevan and Leonard Marks, both from the University of California Los Angeles in the USA, describe the MRI-FIRST trial as “thoughtfully designed,” pointing out that, in contrast to previous trials of MRI-guided biopsy, each patient acted as his own control.

This method “provided a conclusion that was not apparent in […] earlier investigations: although targeting might be somewhat more sensitive than systematic sampling, the combination of the two methods provides the greatest detection,” they say.

Jayadevan and Marks also note that the study reflected real-world implementation of MRI-targeted biopsy, as MRI was conducted locally at each of the 16 participating sites.

They suggest: “At the beginning of a new programme, the sensitivity of targeted biopsy alone might be less than is reported in previous clinical trials. Thus, as elegantly shown in MRI-FIRST, combined biopsy should be considered as the present standard.

“The decision of whether to perform biopsy in the first place will continue to be based on overall clinical suspicion, including palpable abnormalities, family history, race, prostate-specific antigen concentrations, and MRI findings (or lack thereof),” the commentators conclude.

By Laura Cowen

medwireNews is an independent medical news service provided by Springer Healthcare. © 2018 Springer Healthcare part of the Springer Nature group

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