Racial differences in the natural history of small renal masses: A prospective registry study.

Abstract

295 Background: Patients with small renal masses (SRM) can be managed conservatively by active surveillance (AS) or active treatment. A subset of patients who elect for AS undergo delayed intervention, either due to progression or other factors. Using a large, prospective registry of patients with SRMs we characterize differences in SRM growth trajectories on AS and pathologic differences among resected SRMs between African Americans (AA) and Caucasians. Methods: We stratified patients enrolled in the prospective Delayed Intervention and Surveillance for Small Renal Masses (DISSRM) registry by race. DISSRM includes AS, primary intervention (PI), and delayed intervention (DI). The growth rate for patients who elected for AS was compared between AA and Caucasian patients. Pathologic features among patients who underwent PI or DI were compared by race. Results: We enrolled 745 patients in DISSRM who were either AA (n = 117, 15.7%) or Caucasian (n = 628 (84.3%)), with median follow-up of 3.3 years [IQR 1.5-6.6]. 410 patients elected for AS (84% Caucasian, 16% AA) and 401 opted for PI (n = 335) or DI (n = 66) (86% Caucasian, 14% AA). Within the AS cohort, no differences were seen in age, comorbidities, or tumor size, though Caucasians were more male-predominant (60.9% vs. 38.5%, p = 0.001), and body mass index was higher among AA (p = 0.03). Median overall growth rate for AA vs Caucasian was 0.04 cm/year [-0.03-0.3] vs 0.1 cm/year [0-0.33], p = 0.2 (Figure).In the DI arm, median time to intervention was 12.5 months, with HR (AA vs Caucasian) being 0.32 (0.13-0.82), p = 0.02. There were no differences in baseline clinical characteristics or tumor size in the DI or PI arm, however AA were more likely to undergo radical nephrectomy (24.6% vs. 10.4%, p = 0.01). pT stage and grade were similar between groups, and papillary histology was more common among AA (34.1% vs 19.9%, p = 0.007). There were 31 deaths among patients undergoing intervention, which was significantly worse for AA after multivariable adjustment (HR 2.51, p = 0.025). Conclusions: Using the largest prospective registry of SRM, we found the natural history of SRM on AS to be similar between AA and Caucasians. However, histology, surgical approach, and survival differed between groups, with worse OS among AA. Further socioeconomic and molecular analyses will help elucidate biological differences and identify strategies to improve outcomes among patients with SRM.