Estimated volume growth characteristics of renal tumors undergoing active surveillance

The detection rate of incidental renal masses is increasing. Historically these masses have been treated with extirpative surgery. Hence, there is little information on the growth rate, metastatic potential, and natural history of renal tumors. Through active surveillance, we study the natural history of renal masses and determine their growth rate and risk for metastasis.

From 1997 to 2007, active surveillance was offered to select patients with renal masses with no evidence of metastasis. Based on imaging studies from the initial diagnosis to the last follow up, tumor growth rates were determined.

Forty-six patients were studied for a total of 58 masses. Mean age of patients at diagnosis was 64.3 years. Mean Charlson comorbidity score was 5.2 (median 5, range 2-13). Mean follow up period was 22 months (median 17, range 5-121). Mean initial tumor volume was 6.6 cm3 (median 2.7, range 0.03-43.2). Mean growth rate was 1.9 cm3/yr (median 0.1, range -3.8-27.9), and 6.8% had a volume doubling time of less than 1 year. No patient developed radiographic evidence of metastasis or died during follow up. Thirteen patients (15 masses) went onto operative intervention at a mean follow up of 19 months (median 18, range 4-36); 10/15 (67%) revealed renal cell carcinoma and 5/15 (33%) were benign.

In our cohort, negligible growth rates are observed in the vast majority of renal masses undergoing active surveillance, and thus, a carefully selected patient population may be safely managed with active surveillance with serial imaging.