Abstract
PURPOSE: To assess the prognostic significance of sarcomatoid differentiation for surgically treated metastatic renal cell carcinoma (mRCC). METHODS: Patients undergoing cytoreductive nephrectomy for mRCC in our center between 2006 and 2014 were included. All enrolled patients were separated into two groups according to the presence of sarcomatoid differentiation. Clinical and pathological variables were recorded. Student's t test or Chi-square test was applied to compare them. Univariate and multivariate Cox regression were performed to determine independent prognostic factors for oncologic outcomes. RESULTS: Of the 184 patients with mRCC included, 27 (14.7%) patients presented with sarcomatoid differentiation. The presence of sarcomatoid differentiation was associated with higher rates of non-clear cell histology (P = 0.009), higher Fuhrman grade (P < 0.001), higher rates of presenting tumor necrosis (P = 0.005), worse IMDC risk group (P = 0.022), and MSKCC risk group (P = 0.020). Patients with sarcomatoid differentiation showed shorter median progression-free survival and overall survival. Multivariate analysis identified that sarcomatoid differentiation was independently associated with progression-free survival (hazard ratio [HR]: 2.002, 95% CI 1.047-3.828; P = 0.036) and overall survival (HR: 1.922, 95% CI 1.073-3.445; P = 0.028). Sarcomatoid differentiation remained to be independently associated with inferior PFS (HR: 2.097, 95% CI 1.091-4.030; P = 0.026) and OS (HR: 2.245, 95% CI 1.276-3.951; P = 0.005) for clear cell mRCC. CONCLUSION: The presence of sarcomatoid differentiation is independently associated with poor oncologic outcomes for surgically treated mRCC patients. The association remains significant when the subject of study is restricted to clear cell mRCC.