ReviewThe role of active surveillance of small renal masses

- The incidental diagnosis of SRMs has been increasing significantly.
- Most SRMs have a slow growth rate when followed conservatively with serial imaging.
- The risk of progression to metastatic disease during active surveillance is rare (1-2%).
- Active surveillance can be offered to elderly or unfit patients with delayed intervention in those tumors with fast growth.
- Histological characterization of SRMs by percutaneous biopsy is useful for selection of patients for active surveillance.

IntroductionThe use of modern abdominal imaging modalities have led in recent years to an increased incidental diagnosis of small renal masses (SRMs), especially in elderly patients. The natural history of SRMs has been historically poorly understood because most have been traditionally surgically removed soon after diagnosis. However, several studies of active surveillance (AS) of SRMs have been published in the last decade.MethodsA review of English-language publications on AS of SRMs was performed from 1995 to 2015 using the Medline, Embase and Web of Science databases. Fifty-six articles were selected based on their scientific relevance and critically analysed.ResultsWhen followed conservatively with serial imaging, SRMs have variable growth rates with an average of 0.31 cm/year in the largest multicenter analysis. A significant number of SRMs have a slow growth and some have zero growth under surveillance. The risk of progression to metastatic disease during AS is rare (1-2%). Population-based analyses in older patient populations (>75 years) fail to show a benefit in cancer-specific mortality for surgical treatment of SRMs.DiscussionThe standard of care for localized renal tumors is surgery. In elderly or unfit patients with decreased life expectancy, it is reasonable to propose an initial period of AS, with delayed intervention for those tumors which exhibit a fast growth during follow-up. At present AS is not recommended in younger and fit patients and for masses >4 cm at diagnosis outside clinical trials. Percutaneous needle biopsies of renal tumors have the potential to characterize histologically SRMs at diagnosis, thereby providing useful information for the selection of the best suited patients for AS.ConclusionsMost SRMs are benign tumors or RCCs with a relatively indolent clinical behaviour. AS can be offered to patients with SRMs and decreased life expectancy. Prospective series of AS of histologically confirmed RCCs are needed to confirm the long term safety of this conservative approach.