The Association of Platelet Count with Clinicopathological Significance and Prognosis in Renal Cell Carcinoma: A Systematic Review and Meta-Analysis

Objective Elevated platelet count (PC), a measure of systemic inflammatory response, is inconsistently reported to be associated with poor prognosis in patients with renal cell carcinoma (RCC). We conducted a systematic review and meta-analysis to clarify the significance of PC in RCC prognosis. Methods PubMed, Embase, and Web of Science databases were searched to identify eligible studies to evaluate the associations of PC with patient survival and clinicopathological features of RCC. Results We analyzed 25 studies including 11,458 patients in the meta-analysis and categorized the included articles into three groups based on RCC stage. An elevated PC level was associated with poor overall survival (OS, hazard ratio [HR] 2.24, 95% confidence interval [CI] 1.87-2.67, P < 0.001) and cancer-specific survival (CSS, HR 2.59, 95% CI 1.92-3.48, P < 0.001) when all stages were examined together; with poor CSS (HR 5.09, 95% CI 2.41-10.73, P < 0.001) and recurrence-free survival (HR 6.68, 95% CI 3.35-13.34, P < 0.001) for localized RCC; with poor OS (HR 2.00, 95% CI 1.75-2.28, P < 0.001) for metastatic RCC; and with poor OS (HR 2.05, 95% CI 1.04-4.03, P = 0.038), CSS (HR 3.38, 95% CI 1.86-6.15, P < 0.001), and PFS (HR 2.97, 95% CI 1.47-6.00, P = 0.002) for clear cell RCC. Furthermore, an elevated PC level was significantly associated with TNM stage (OR 3.11, 95% CI 1.59-6.06, P = 0.001), pathological T stage (OR 3.13, 95% CI 2.60-3.77, P < 0.001), lymph node metastasis (OR 4.01, 95% CI 2.99-5.37, P < 0.001), distant metastasis (OR 3.85, 95% CI 2.46-6.04, P < 0.001), Fuhrman grade (OR 3.70, 95% CI 3.00-4.56, P < 0.001), tumor size (OR 4.69, 95% CI 2.78-7.91, P < 0.001) and Eastern Cooperative Oncology Group score (OR 5.50, 95% CI 3.26-9.28, P < 0.001). Conclusion An elevated PC level implied poor prognosis in patients with RCC and could serve as a readily available biomarker for managing this disease.