Comparison of oncologic outcomes between sarcomatoid and clear cell renal cell carcinoma

Background: Sarcomatoid renal cell carcinoma (sRCC) is a rare histological subtype that is associated with unfavorable prognosis. We sought to examine the effect of sRCC on cancer-specific mortality (CSM) relative to clear cell renal cell carcinoma (ccRCC), after adjusting for other variables, as well as other-cause mortality (OCM). Methods: We relied on the Surveillance, Epidemiology, and End Results–Medicare database from 2000 to 2009 to identify a cohort of 7916 patients with either sRCC (n = 234) or ccRCC (n = 7682) who received surgery as primary treatment. Patient, tumor, and treatment characteristics were evaluated. Then, 5-year smoothed Poisson regression CSM and OCM estimates were generated for stage-by-stage comparisons between sRCC and ccRCC. A multivariable competing-risks regression model predicting CSM and adjusting for several patient and tumor characteristics, as well as OCM, was finally fitted. Results: Compared to ccRCC patients, sRCC patients had more advanced and more aggressive disease at diagnosis. Specifically, 48 and 7 % of sRCC and ccRCC patients presented with stage IV disease, respectively (p <0.001). Overall, 5-year CSM and OCM estimates were 67 and 17 % for sRCC patients and 14 and 19 % for ccRCC patients. In stage-by-stage analyses, sRCC was invariably associated with worse CSM. After adjusting for several characteristics as well as OCM, sRCC was associated with a 3.2 higher risk of CSM compared with ccRCC. Conclusions: Patients with sRCC are present with more advanced disease. Moreover, sRCC is associated with a higher rate of CSM, even after adjusting for several characteristics and OCM.