Growth kinetics and active surveillance for small renal masses

Management options for small renal masses (SRMs) include excision, ablation, and active surveillance. Increasing interest in active surveillance, particularly for tumors of limited oncologic potential, in patients with other significant health concerns continues to rise, but precise protocols are still lacking.

A review of 18 retrospective series of patients undergoing active surveillance for 957 SRMs indicates that the majority grew during observation (mean 0.32  cm/year), but only 1.4% metastasized during 32 months of follow-up (median). One published prospective series of 209 SRMs reported average growth of 0.13  cm/year and only 1% metastasized. Maximal tumor diameter (or volume) at presentation is a predictor of growth rate, high-grade disease, and likelihood of metastasis. SRMs less than 3  cm are very unlikely to metastasize and deferring treatment has not been associated with increased failure to cure.

Active surveillance is a reasonable initial strategy in most patients with SRMs, particularly those with limited life-expectancy and increased perioperative risk. Intervention should be considered for growth to greater than 3-4  cm or by greater than 0.4-0.5  cm/year while on active surveillance.