Surgical removal of renal tumors with low metastatic potential based on clinical radiographic size: A systematic review of the literature

Introduction: Many patients with small renal masses (SRM) undergo surgical resection of benign and potentially indolent renal masses. We review the available literature to quantify the proportion of renal tumors that are low-risk based on clinical radiographic size, and quantify the number of low-risk masses surgically removed in the United States. Methods: We systematically reviewed the literature for studies including pathologic findings after excision of renal masses. Inclusion criteria required studies capture both benign and malignant histology at surgical pathology, tumor grade, and stratification by radiographic tumor size. We queried our institutional database using the same parameters. Meta-analysis results were applied to SEER incidence and management data for renal masses. Very-low-risk tumors were defined as benign or grade 1 cT1a, and low-risk tumors as benign, grade 1, or grade 2 cT1a. Results: A total of 733 titles were reviewed at title screening with 6 full text articles and our institutional database included for meta-analysis. Pooled estimates of benign, very-low-risk, and low-risk tumors were stratified by tumor size: <= 2 cm (25.5%, 40.1%, and 89.3%), 2 to 3 cm (21.2%, 34.1%, and 84.5%), 3 to 4 cm (16.1%, 26.6%, and 77.1%), 4 to 6 cm (11.9%, 23.8%, and 66.4%), and >6 cm (7.2%, 12.6%, and 50.3%). An estimated 3,300 benign, 5,400 very-low-risk, and 13,600 low-risk SRMs were resected in 2014 in the United States. Conclusion: A substantial portion of patients with SRM are undergoing surgical excision despite harboring tumors of low metastatic potential. The rate of high-grade histology increased with increasing clinical radiographic size, which can be used in counseling and decision- making regarding placement on active surveillance. The number of low-risk SRM removed annually in the United States increased from 8,500 in 2000 to 13,600 in 2014 with stabilization in recent years. (C) 2019 Elsevier Inc. All rights reserved.