Growth kinetics and active surveillance for small renal masses

Area of Science:

• Urology
• Oncology
• Nephrology

Background:

• Small renal masses (SRMs) management includes surgery, ablation, and active surveillance.
• Active surveillance is gaining traction for SRMs with low oncologic potential, especially in patients with comorbidities.
• Standardized protocols for active surveillance of SRMs are still under development.

Purpose of the Study:

• To review current evidence on active surveillance for small renal masses (SRMs).
• To evaluate the safety and efficacy of active surveillance as an initial management strategy for SRMs.
• To identify predictors of growth and metastasis in SRMs managed with active surveillance.

Main Methods:

• Systematic review of 18 retrospective series and one prospective series on SRMs managed with active surveillance.
• Analysis of tumor growth rates, metastasis rates, and factors influencing outcomes.
• Evaluation of patient characteristics, including life expectancy and perioperative risk.

Main Results:

• The majority of SRMs (957 cases) demonstrated growth during active surveillance (mean 0.32 cm/year), with a low metastasis rate (1.4% over 32 months median follow-up).
• A prospective series (209 SRMs) reported slower growth (0.13 cm/year) and a 1% metastasis rate.
• Maximal tumor diameter predicts growth rate, high-grade disease, and metastasis risk. SRMs <3 cm rarely metastasize, and delayed treatment does not increase cure failure.

Conclusions:

• Active surveillance is a reasonable initial approach for most SRMs, particularly in patients with limited life expectancy or high surgical risk.
• Intervention for SRMs on active surveillance should be considered if tumors grow beyond 3-4 cm or at a rate exceeding 0.4-0.5 cm/year.