Natural history, role of biopsy, and active surveillance of renal masses

With the increased utilization of abdominal imaging, we have witnessed a significant increase in incidentally detected clinically localized, small renal masses (SRMs) over the past few decades. While extirpation has remained the gold standard in managing SRMs, mortality rates from kidney cancer remain relatively unchanged. This suggests that a proportion of small renal masses may be indolent tumors that do not require surgical intervention. From these observations, active surveillance (AS) has emerged as an alternative management strategy in select patients with significant competing risks. The use of AS has provided the basis for describing the natural history of renal masses managed expectantly. Although the data are limited, we have observed that many incidental renal masses demonstrate slow growth kinetics with a low rate of progression to metastatic disease over an intermediate time period. While judicious use of AS in carefully selected patients appears to be a viable management strategy, prospective trials are necessary to define entry and intervention criteria for existing AS protocols.