Purpose: We assessed the added value of concomitant systematic biopsy for final grade group prediction in patients with positive magnetic resonance imaging who were undergoing targeted biopsy.
Materials and methods: Included in study were 478 consecutive patients with prebiopsy positive multiparametric magnetic resonance imaging and a greater than 10-core systematic biopsy combined with fusion targeted biopsy who underwent radical prostatectomy. The primary end point was the grade group concordance between biopsy and radical prostatectomy pathology according to the biopsy technique. Clinical and biological factors associated with the performance of systematic biopsy were analyzed.
Results: Adding systematic biopsy to targeted biopsy modified the d'Amico risk classification toward more intermediate and high risk in 7.8% of cases, mainly from low to intermediate risk with low risk prostate cancer on targeted biopsy in 44.3%. This reclassification was significantly higher in patients with lower prostate specific antigen and with prostate specific antigen density less than 0.20 ng/ml/gm (11.7% vs 2.4%, p <0.001). The concordance rate between biopsy pathology and radical prostatectomy pathology significantly differed between targeted biopsy and targeted biopsy plus systematic biopsy (45.2% and 51.7%, respectively). The upgrading rate in radical prostatectomy specimens decreased by 22% when systematic biopsy was added to targeted biopsy. Patients in whom systematic biopsy did not modify grading were more likely to have pT3-4 and/or pN1 disease on final pathology (56.9% vs 38.3%, p=0.007).
Conclusions: Grading concordance between biopsy pathology and radical prostatectomy pathology was improved by adding systematic biopsy in all patient subgroups. Patients with prostate specific antigen density less than 0.20 ng/ml/gm benefited the most from this combined biopsy strategy. Systematic biopsy reclassified a nonnegligible number of cases toward a higher risk category, mainly the low risk cases. Thus, systematic biopsy could modify treatment decision making.
Keywords: biopsy; magnetic resonance imaging; prostatectomy; prostatic neoplasms; risk.