The natural history of renal functional decline in patients undergoing surveillance in the DISSRM registry.

OBJECTIVE

To describe the natural history of renal function in patients on active surveillance (AS) for small renal masses (SRM) in the Delayed Intervention and Surveillance for Small Renal Masses Registry.

METHODS

Delayed Intervention and Surveillance for Small Renal Masses is a prospective, multi-institutional registry of patients with SRM (≤ 4 cm) who choose intervention or AS. Of these, 64 patients on AS had longitudinal serum creatinine (sCr) values and underwent analysis of estimated glomerular filtration rate (eGFR). eGFR was calculated using the Modification of Diet in Renal Disease formula. The Kidney Disease Outcomes Quality Initiative chronic kidney disease (CKD) classification was used to categorize patients' eGFR values.

RESULTS

Median age was 74 (range: 34-88) years at onset of AS. Overall, 9% (6/64) of patients had CKD at baseline. Median initial tumor size was 2.1cm (range: 0.8-4.0). Median Charlson comorbidity index score was 4 (range: 0-8). Median baseline sCr was 1.0mg/dl (range: 0.4-2.1) and median baseline eGFR was 70.25 (range: 24.07-165.52). After a median follow-up of 17 (range: 2-46) months, 64% of patients experienced a decrease in eGFR, with average yearly decrease in eGFR of 1.82 ml/min/1.73 m(2) (P = 0.092) and average yearly increase in sCr of 0.046 (P = 0.012). A total of 15 (24%) patients experienced an upstaging in classification of CKD.

DISCUSSION

Nearly two-thirds of patients on AS experienced a decrease in eGFR and nearly one-fourth had upstaging of CKD classification. The annual eGFR decline experienced by patients on AS minimally exceeded the annual decline of 1.49 ± 0.3 ml/min/1.73 m(2) that an individual who was 70 to 79 years of age can expect from aging alone. Further follow-up is necessary to assess this in a more definitive manner, but this trend should be considered when evaluating AS as an alternative to interventional therapies for SRM.