CA9 and renal cell carcinoma: Thus, this meta-analysis aimed to clarify the prognostic role of CAIX in RCC; the results suggest that low CAIX expression is associated with poor DSS (HR  = 1.89, 95% CI: 1.20–2.98, P = 0.006), worse OS (HR = 2.03, 95% CI: 1.28–3.21, P = 0.002) and unfavorable PFS (HR = 2.62, 95% CI: 1.14–6.05, P = 0.02).