LAUSR

e22519 Background: RCS are rare soft tissue sarcomas and account for 0.8-2.7% of malignant kidney tumors. Level 1 evidence guiding optimal patient management is lacking due to the rarity of this disease. Utilizing the NCDB, we analyzed prognostic factors, the current treatment patterns and outcomes in patients with RCS in the United States. Methods: The NCDB was queried from 2004- 2015 for patients diagnosed with MRCS. Baseline patient characteristics were summarized using descriptive statistics. Impact of baseline demographic, Clinicopathologic variables and treatment on overall survival (OS) was evaluated using univariate (UV) and multivariable (MV) cox proportional hazards analysis. Results: 454 patients diagnosed with MRCS between 2004- 2015 were included in this analysis. Median age at diagnosis was 63. Males (62%) had higher incidence of RCS compared with females. 86% (n = 389) were Caucasian, while only 9.5% (n = 43) were African American. Right and left kidneys were equally affected. Spindle cell sarcoma was the most common histology (n = 276). 37.5% (n = 170) underwent CN. 49% of patients received chemotherapy (n = 216) and 24% received radiation therapy (n = 109). Overall, 48% (n = 82) of patients who underwent nephrectomy had chemotherapy. Median OS was 4.5 months (3.8-5.2 mos.). On UV analysis age ≥ 55 years (HR: 1.92, p < 0.001), no systemic treatment (HR: 1.91, P < 0.01), and no CN (HR: 2.1, p < .001) had worse OS. On MV analysis, patients who did not undergo CN had significantly worsened OS compared to CN (7.56 vs 3.35 mos., HR-1.91, CI: 1.52- 2.41 p < 0.001). Patients who received chemotherapy after CN had a better OS (13.3 vs 3.7 mos., p < 0.001). Conclusions: MRCS is an aggressive malignancy with a median OS of less than 5 months. Age at diagnosis, CN and systemic therapy had a statistically significant impact on OS. Given the rarity of the tumor and inadequacy of guidelines, these results can be considered in making management decisions. We understand the limitations of a registry-based study and hence, prospective multi-national clinical trials are essential to further guide us on management of this rare tumor. [Table: see text]