Purpose: Serial biopsy is a mainstay for patients on active surveillance (AS) for prostate cancer. multiparametric MRI targeting has become a standard. It is unclear whether targeted biopsy alone reliably identifies the dominant lesion, thereby obviating the need for systematic sampling.
Materials and methods: Participants enrolled in AS with early-stage prostate cancer (PSA <20, cT1-2, GG1-2) and underwent 2+ systematic biopsy sessions with or without magnetic resonance (MR)-targeted sampling. The findings for dominant Gleason Grade Group (GG) and tumor localization were assessed.
Results: Among 821 men who underwent MR fusion biopsies, 82% were diagnosed with GG1 and 18% with GG2. Sixty-two percent had their first MR fusion biopsy as diagnostic or confirmatory. Across all fusion biopsies, MRI-targeted detection of GG and/or tumor location overlapped with systematic sampling for 95% of cases. For 5% of cases, systematic biopsy was unique in detecting GG and location outside the target. Most unique lesions detected outside the target had marginally aggressive features: 73% GG2 of low-volume and favorable histologic subtypes.
Conclusions: In men with MR fusion biopsies, targeting alone identified the dominant GG and location most of the time (95%); 25% of dominant lesions were contiguous to the target, suggesting that better sampling of the target improves detection. The remaining 5% of men had higher-grade, low-volume disease outside the targeted lesion, of which only 2% had aggressive risk features. MR fusion targeting, without systematic sampling, may be sufficient to monitor men on AS. Few high-risk cancers are missed, all of limited volume and favorable histology.
Keywords: MR fusion; active surveillance; prostate cancer; systematic biopsy; targeted biopsy.