Active surveillance of renal cortical neoplasms: a contemporary review

Over the past 2 decades, there has been a significant increase in the number of incidentally found small renal cortical neoplasms (RCNs). As more RCNs are being discovered in the elderly and infirmed patient populations, there has been a growing interest in the role of active surveillance (AS). Active surveillance is recommended for high surgical-risk patients and those with a reduced life expectancy. It is also an option for patients wishing to avoid surgery. We review the current literature on AS and highlight the natural history of disease, the important factors to evaluate during AS, and the contemporary role of biopsy.

The MEDLINE database was searched using PubMed. Search terms included active surveillance, renal mass, natural history, and renal mass histology. From 1966 to present, 17 AS series were identified, all of which have been included in this summary. A summary was performed by compiling all available data and performing a weighted mean where applicable.

Initial tumor size does not correlate with growth rate or malignancy. The mean growth rate in large published series is low (0.28-0.34 cm/year). Tumors with high growth rates usually represent malignant lesions and typically undergo delayed intervention. Progression to metatatic disease is a low-probability event for tumors on AS (1.4%); however, this is still a risk that patients must be willing to accept. Larger tumors (cT1b and cT2) also demonstrate relatively low growth (0.57 cm/year); however, these tumors should be monitored carefully. Tumors followed for > 5 years demonstrate a low growth rate (0.15 cm/year), will not likely require intervention, and have a low chance of progression to metastatic disease.

For highly selected patients with RCN, AS is a reasonable treatment option. Age, surgical risk, comorbidities, and patient opinion must all factor into the final decision when considering a patient for AS.