Active Surveillance for Risk Stratification of All Small Renal Masses Lacking Predefined Clinical Criteria for Intervention.

PURPOSE: Despite general indolence of small renal masses and no known adversity from treatment delays, broad usage of active surveillance as a means to risk-stratify patients with small renal masses for more selective treatment has not been studied. We describe outcomes for a novel approach in which active surveillance was recommended to all patients with small renal masses lacking predefined progression criteria for intervention.
MATERIALS AND METHODS: All nondialysis dependent patients with nonmetastatic small renal masses seen by 1 urologist at a comprehensive cancer center during January 2013-September 2017 were managed with active surveillance if standardized progression criteria for intervention were absent, with delayed intervention recommended only upon progression criteria for intervention development. Progression criteria for intervention were defined prospectively as small renal mass-related symptoms, unfavorable histology, cT3a stage or either of the following without benign neoplastic biopsy histology: longest tumor diameter >4 cm; growth rate >5 mm/year for longest tumor diameter ≤3 cm or >3 mm/year for longest tumor diameter >3 cm.
RESULTS: In all, 96% (123/128) of patients with small renal masses lacked progression criteria for intervention at presentation and underwent active surveillance. With median/mean 31/34 months followup, none developed metastasis and 30% (37/123) developed progression criteria for intervention, 78% (29/37) of whom underwent delayed intervention. One (1%) patient crossed over to delayed intervention without progression criteria for intervention. Three-year progression criteria for intervention-free and delayed intervention-free rates were 72% and 75%, respectively. Delayed intervention resections were enriched (62%) for pT3 and/or nuclear grade 3-4 malignant pathology, with no benign resections.
CONCLUSIONS: Active surveillance using predefined progression criteria for intervention in otherwise unselected patients with small renal masses allows intervention to be focused on at-risk small renal masses with common adverse pathology, avoiding treatment for most patients with small renal masses. Long-term delayed intervention and oncologic safety require study.