Prognostic significance of systemic immune-inflammation index in patients with clear cell renal cell carcinoma after nephrectomy

Objective To investigate the prognostic value of systemic immune-inflammation index (SII) in patients with clear cell renal cell carcinoma after nephrectomy. Methods Clinicopathologic data of 1228 patients with clear cell renal cell carcinoma who underwent radical nephrectomy at Peking University First Hospital between January 2001 and December 2010 were retrospectively analyzed. Hematological features were collected within one week before surgery. Receiver operating characteristic (ROC) curve was generated to explore the sensitivity and specificity of SII, and the maximum Youden index was used to determine the optimal cut-off value of SII. The primary endpoint was cancer specific survival (CSS). Kaplan-Meier survival analysis and Cox proportional regression were performed to explore the prognostic factors of CSS. Results According to the ROC curve and Youden index, the optimal cut-off value of SII was 602.66. Based on this cutoff value, the patients were divided into either a high (SII≥602.66) or a low SII group (SII<602.66). Clinicopathologic characteristics associated with higher SII included older age, higher American Society of Anesthesiologists score, higher grade, higher T stage, lymph node metastasis, distant metastasis, tumor with sarcomatoid differentiation, tumor necrosis, lymphovascular invasion, anemia, higher neutrophil to lymphocyte ratio, and higher platelet to lymphocyte ratio. The median follow-up time of the 1228 patients was 69.0 months (IQR 45.0-74.0), and 122 (9.9%) patients died of tumor at last follow-up. The five year cancer specific survival rate of the 1228 patients was 90.72%. According to the results of univariate Kaplan-Meier survival analysis and log-rank test, higher SII value, higher grade, higher T stage, lymph node metastasis, distant metastasis, tumor with sarcomatoid differentiation, tumor necrosis, lymphovascular invasion, anemia, higher neutrophil to lymphocyte ratio, and higher platelet to lymphocyte ratio were all unfavorable factors for CSS. Multivariate Cox proportional regression indicated that higher grade (HR=2.115, 95%CI 1.378-3.246, P=0.001), higher T stage (HR=3.591, 95%CI 2.278-5.661, P<0.001), lymph node metastasis (HR=2.169, 95%CI 1.239-3.800, P=0.007), distant metastasis (HR=5.590, 95%CI 3.636-8.595, P<0.001), higher SII value (HR=1.788, 95%CI 1.212-2.637, P=0.003) were all independent prognostic factors for CSS. Conclusion Higher SII is associated with worse CSS in patients with clear cell renal cell carcinoma after nephrectomy. Key words: Renal cell carcinoma; Nephrectomy; Systemic immune-inflammation index; Prognosis