Does Overgrading on Targeted Biopsy of Magnetic Resonance Imaging-visible Lesions in Prostate Cancer Lead to Overtreatment?

Background and Objective: Targeted biopsy of the index prostate cancer (PCa) lesion on multiparametric magnetic resonance imaging (MRI) is effective in reducing the risk of overdiagnosis of indolent PCa. However, it remains to be determined whether MRI-targeted biopsy can lead to a stage shift via overgrading of the index lesion by focusing only on the highest-grade component, and to a subsequent risk of overtreatment. Our aim was to assess whether overgrading on MRI-targeted biopsy may lead to overtreatment, using radical prostatectomy (RP) specimens as the reference standard.
Methods: Patients with clinically localized PCa who had positive MRI findings (Prostate Imaging-Reporting and Data System [PI-RADS] score ≥3) and Gleason grade group (GG) ≥2 disease detected on MRI-targeted biopsy were retrospectively identified from a prospectively maintained database that records all RP procedures from eight referral centers. Biopsy grade was defined as the highest grade detected. Downgrading was defined as lower GG for the RP specimen than for MRI-targeted biopsy. Overtreatment was defined as downgrading to RP GG 1 for cases with GG ≥2 on biopsy, or to RP low-burden GG 2 for cases with GG ≥3 on biopsy.
Key Findings and Limitations: We included 1020 consecutive biopsy-naïve patients with GG ≥2 PCa on MRI-targeted biopsy in the study. Pathological analysis of RP specimens showed downgrading in 178 patients (17%). The transperineal biopsy route was significantly associated with a lower risk of downgrading (odds ratio 0.364, 95% confidence interval 0.142-0.814; p = 0.022). Among 555 patients with GG 2 on targeted biopsy, only 18 (3.2%) were downgraded to GG 1 on RP. Among 465 patients with GG ≥3 on targeted biopsy, three (0.6%) were downgraded to GG 1 and seven were downgraded to low-burden GG 2 on RP. The overall risk of overtreatment due to targeted biopsy was 2.7% (28/1020).
Conclusions and Clinical Implications: Our multicenter study revealed no strong evidence that targeted biopsy results could lead to a high risk of overtreatment.
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