MP54-04 PARTIAL NEPHRECTOMY IS EQUIVALENT TO ACTIVE SURVEILLANCE IN PRESERVING RENAL FUNCTION FOR PATIENTS WITH SMALL RENAL MASSES

Abstract

INTRODUCTION AND OBJECTIVES: Active surveillance (AS) for patients with a small renal mass (SRM) is considered an acceptable alternative to surgery due to the slow growth of such tumors, low risk of metastasis, and presumed retention of renal function. We previously demonstrated a moderate decline in renal function for patients on AS in the Delayed Intervention and Surveillance for Small Renal Masses (DISSRM) Registry. We now sought to compare this with the decline following extirpative modalities. We also correlated tumor growth rate with renal functional decline in AS patients. METHODS: The multi-institutional DISSRM Registry opened January 1, 2009. Patients with SRMs 4cm were entered into AS or intervention arms. Those electing AS followed an imaging protocol. Growth rates of masses were calculated based on changes in diameter. GFR was calculated with the Modification of Diet in Renal Disease formula. GFR change was calculated from the first value for surveillance patients or the pre-operative value for intervention patients, to the most recent value. Linear regression was used to determine the effects of study arm and growth rate on GFR, while controlling for the impact of demographics, comorbidities, and tumor histology. RESULTS: The difference in average GFR decline between the 66 partial nephrectomy (PN) patients and the 67 AS patients was not significant (1.9 vs 0.5, p1⁄40.270). In contrast, there was a significantly greater decline in the 15 radical nephrectomy (RN) patients compared to the AS patients (9.2 vs 0.5, p1⁄40.001). Average follow up time for AS, PN, and RN patients was 20, 19, and 16 months, respectively. On regression analysis while controlling for comorbidities, GFR was again found to decline faster in RN (p1⁄40.016) but not PN (p1⁄40.778) patients compared to AS patients. Average growth rate of masses in the AS arm was 0.19 cm/year. There was no significant difference in GFR change between AS patients whose tumors increased in size over their enrollment and those whose tumors decreased in size, as shown in the table (p1⁄40.260). On regression analysis the tumor growth rate did not significantly affect the rate of GFR decline while controlling for comorbidities (p1⁄40.915). CONCLUSIONS: AS for the small renal mass yields equivalent preservation of GFR when compared to PN, while both modalities are superior to RN. Preservation of renal function during AS is unaffected by growth rate. These renal function outcomes should be considered when making treatment decisions. N GFR Declined No change in GFR GFR Rose