Current controversies with active surveillance management of small renal masses.

Active surveillance (AS) management for patients with small renal masses (SRMs) is increasing globally, but questions remain regarding optimal AS practice. This review provides an evidence-based perspective on current controversies in SRM AS management. Considerable variation in AS utilization likely reflects non-standardization of patient selection criteria and differences among providers and healthcare settings. While most expert-consensus guidelines still restrict AS candidacy to patients with very small (< 1-2cm) renal tumors or significant health issues, increasing research supports AS to be an acceptable option for tumors up to 4 cm and a preferred option for many tumors up to 2 cm. For younger patients, AS appears oncologically safe but efficacy for long-term avoidance of delayed intervention (DI) remains unknown. Progression definitions for triggering DI still lack standardization, but there is general consensus for including thresholds based on some or all "GLASS" criteria [Growth rate; Longest tumor diameter; Adverse biopsy histology; Stage (≥ cT3a); Symptomatology]. SRM biopsy during AS can diagnose benign neoplasm with high accuracy to negate the need for DI, particularly when corroborated by computed tomography (CT) enhancement-based approaches such as tumor:cortex Peak Early Enhancement Ratio (PEER) scoring. In contrast, the value for biopsy in adverse histology detection remains more controversial. Advanced imaging modalities, including 99mTc-sestamibi single photon emission computed tomography (SPECT)/CT and [89Zr]Zr-girentuximab positron emission tomography (PET)/CT, may serve as useful adjuncts to biopsy during AS, while providing limited accuracy alone when biopsy is deferred. Future investigative efforts should focus on standardizing AS protocols, refining progression criteria for intervention, and addressing uncertainties about longer-term outcomes, particularly in younger patients.