Utilization and contemporary results of renal mass biopsy.

Abstract

623 Background: Renal mass biopsy (RMB) for localized renal masses (RM) is being re-evaluated to improve risk stratification and minimize morbidity from over-treatment. We review our institutional experience with RMB to identify performance characteristics and highlight opportunities to improve management. Methods: Using our prospectively maintained database, we identified patients who underwent core RMB +/- fine needle aspiration (FNA). We describe performance characteristics and assess pathologic concordance. Using the University of Michigan (UM) algorithm, we reviewed the potential that RMB influenced therapeutic decision-making. Results: We noted 374 RMBs performed from 1999-2015 (66% within last 5 years). Core RMB (+/- FNA) was performed in 65.2% (244/374) of cases, of which 41% (99/244) underwent surgical resection. Initial core RMB was non-diagnostic in 9% (9/99) of surgical cases and subsequently diagnosed with RCC. RCC diagnosed on core RMB that underwent surgical resection demonstrated histologic and grade concordance of 94.3% and 62.5%. All discordant grades were upgraded at surgery. 11% of all RMB were benign and no surgical intervention occurred. In our cohort, 19% of all RMB patients treated surgically had tumors classified as favorable or intermediate < 2cm using the UM algorithm and might otherwise have been candidates for AS. Conversely, 42% of all surgically treated patients had UM favorable characteristics but had tumors > 4cm and therefore underwent surgical resection based on size criteria in the context of RMB results. Conclusions: RMB is effective in the evaluation of RM with minimal morbidity. Our histologic/grade concordance is consistent with published data and underscores that RMB harbors clinical uncertainties. Clinical management pathways incorporating RMB may decrease over-treatment but also may risk under-treatment based on poor grade concordance. Using the UM algorithm, 30% of lesions in our cohort were AS candidates after RMB (over-treatment risk). Conversely, 18% of surgically treated lesions were UM AS candidates after RMB and upgraded on final pathology, demonstrating the risk of under treatment. RMB may be considered in patients where results would influence clinical decision-making.