The prognostic value and clinicopathological features of sarcomatoid differentiation in patients with renal cell carcinoma: a systematic review and meta-analysis

BACKGROUND AND PURPOSE: Numerous studies have demonstrated that sarcomatoid differentiation is linked to the risk of renal cell carcinoma (RCC). However, its actual clinicopathological impact remains inconclusive. Therefore, we undertook a meta-analysis to evaluate the pathologic and prognostic impacts of sarcomatoid differentiation in patients with RCC by assessing cancer-specific survival, overall survival, recurrence-free survival, progression-free survival, and cancer-specific mortality. MATERIALS AND METHODS: In accordance with the preferred reporting items for systematic reviews and meta-analysis statement, relevant studies were collected systematically from PubMed, Embase, and Web of Science to identify relevant studies published prior to January 2018. The pooled effects (hazard ratios, odds ratios, and standard mean differences) and 95% confidence intervals were calculated to investigate the association of sarcomatoid differentiation with cancer prognosis and clinicopathological features. RESULTS: Thirty-five studies (N=11,261 patients [n=59–1,437 per study]) on RCC were included in this meta-analysis. Overall, the pooled analysis suggested that sarcomatoid differentiation was significantly associated with unfavorable cancer-specific survival (HR=1.46, 95% CI: 1.26–1.70, p<0.001), overall survival (HR=1.59, 95% CI: 1.42–1.78, p<0.001), progression-free survival (HR=1.61, 95% CI: 1.35–1.91, p<0.001), recurrence-free survival (HR=1.60, 95% CI: 1.29–1.99, p<0.001), and cancer-specific mortality (HR=2.36, 95% CI: 1.64–3.41, p<0.001) in patients with RCC. Moreover, sarcomatoid differentiation was closely correlated with TNM stage (III/IV vs I/II: OR=1.84, 95% CI: 1.12–3.03, p=0.017), Fuhrman grade (III/IV vs I/II: OR=8.37, 95% CI: 2.92–24.00, p<0.001), lymph node involvement (N1 vs N0: OR=1.88, 95% CI: 1.08–3.28, p=0.026), and pathological types (clear cell RCC-only vs mixed type: OR=0.48, 95% CI: 0.29–0.80, p=0.005), but was not related to gender (male vs female, OR=0.86, 95% CI: 0.58–1.28, p=0.464) and average age (SMD=−0.02, 95% CI: −0.20–0.17, p=0.868). CONCLUSION: This study suggests that sarcomatoid differentiation in histopathology is associated with poor clinical outcome and advanced clinicopathological features in RCC and could serve as a poor prognostic factor for RCC patients.