Multiparametric magnetic resonance imaging and fusion biopsy detect more high risk prostate cancer and less low risk prostate cancer than systematic biopsy. However, there remains a small subset of patients in whom systematic biopsy captures higher grade disease than fusion biopsy. We sought to identify potential mechanisms of the failure of fusion biopsy in the detection of clinically significant prostate cancer.Materials and Methods:
We reviewed a prospectively maintained database of patients who underwent multiparametric magnetic resonance imaging followed by fusion biopsy and systematic biopsy from 2007 to 2014. In patients in whom disease was upgraded to clinically significant disease (Gleason 7 or greater) by systematic biopsy over fusion biopsy, independent re-review of magnetic resonance imaging, archived biopsy imaging and whole mount pathology as well as needle coordinate mapping were performed. Multivariate logistic regression analysis was done to determine predictors of upgrading by systematic biopsy.Results:
Disease was upgraded based on systematic biopsy over fusion biopsy in 135 of 1,003 patients (13.5%), of whom only 62 (6.2%) were upgraded to intermediate (Gleason 7) and high risk (Gleason 8 or greater) prostate cancer (51 or 5.1% and 11 or 1.1%, respectively). On multivariate analysis lower prostate specific antigen (p <0.001), higher magnetic resonance imaging prostate volume (p <0.001) and a lower number of target cores (p = 0.001) were predictors of upgrading by systematic biopsy. Main mechanisms of under grading by fusion biopsy included multiparametric magnetic resonance imaging reader oversight, presence of magnetic resonance imaging invisible cancer, fusion biopsy technique error and intralesion Gleason heterogeneity.Conclusions:
Magnetic resonance imaging and fusion biopsy rarely missed clinically significant prostate cancer as only 62 of 1,003 cases (6.2%) were upgraded to clinically significant disease by systematic biopsy. Imaging and biopsy techniques are continually refined. Further studies will help clarify mechanisms of fusion biopsy failure and the patient populations that benefit from systematic biopsy in addition to fusion biopsy.