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Table 3 Cox proportional hazard regression analyses of clinicopathological factors and piRNAs for predicting overall and recurrence-free survival in ccRCC patients after nephrectomy and C-indexes of the models

From: Piwi-interacting RNAs as novel prognostic markers in clear cell renal cell carcinomas

  Overall survival analysisa Recurrence-free survival analysisa
  All ccRCC patients (N = 106) Non-metastatic ccRCC (N = 76) Non-metastatic ccRCC (N = 72)
Variableb HR (95 % CI) P value HR (95 % CI) P value HR (95 % CI) P value
Univariate analysis
Age (continuous) 0.98 (0.961.01) 0.300 0.99 (0.941.04) 0.771 1.01 (0.971.05) 0.709
Gender 0.97 (0.462.04) 0.929 2.95 (0.3922.8) 0.297 5.35 (0.7239.8) 0.103
pT stage (pT1-2/pT3-4) 4.44 (2.149.93) <0.0001 3.57 (1.1311.3) 0.031 3.47 (1.378.78) 0.009
Grade (G1-2/G3-4) 7.75 (3.9115.4) <0.0001 17.3 (3.6781.3) 0.003 4.73 (2.279.84) <0.0001
Margin (R0/R1-2) 2.51 (1.444.38) 0.001 3.15 (0.8212.2) 0.098 6.23 (2.6614.6) <0.0001
Tumor size (continuous) 1.01 (1.011.02) <0.0001 1.01 (1.011.02) 0.020 1.01 (1.011.02) <0.0001
Metastasis 11.6 (5.6024.2) <0.0001 - - - -
piR-30924 2.90 (1.364.94) 0.004 3.11 (1.013.50) 0.049 2.89 (1.048.08) 0.044
piR-57125 0.30 (0.150.59) 0.0006 0.0 0.964 2.08 (0.825.25) 0.123
piR-38756 3.96 (1.878.37) 0.0003 5.40 (1.4719.9) 0.012 2.66 (1.066.67) 0.038
Multivariate analysisc
T stage 0.72 (0.242.15) 0.718 1.42 (0.306.81) 0.658 1.57 (0.386.52) 0.536
Grade 1.17 (0.433.18) 0.760 8.32 (0.5233.4) 0.135 7.75 (1.1154.4) 0.039
Margin 1.57 (0.673.69) 0.298 1.08 (0.196.14) 0.935 2.50 (0.778.15) 0.127
Tumor size 1.00 (0.991.02) 0.603 0.99 (0.971.02) 0.457 1.00 (0.991.02) 0.743
Metastasis 8.41 (3.1022.8) <0.0001 - -   
piR-30924 2.04 (1.024.51) 0.046 1.10 (0.245.03) 0.899 1.50 (0.415.43) 0.540
piR-57125 0.50 (0.211.18) 0.112 - -   
piR-38756 1.93 (0.725.16) 0.190 5.42 (0.9929.8) 0.052 3.15 (1.969.32) 0.038
 C-Index with all variablesd 0.854   0.759   0.803  
 C-Index without piRNAs 0.835   0.589   0.753  
Multivariate analysis, backward eliminatione
Metastasis 11.0 (4.8225.3) <0.0001 - - - -
Grade - - 8.00 (1.2053.4) 0.032 27.8 (6.60113) <0.0001
piR-30924 2.27 (1.134.58) 0.022 - - - -
piR-57125 0.44 (0.210.93) 0.031 - - - -
piR-38756 - - 5.67 (1.1428.1) 0.034 3.22 (1.168.94) 0.025
 C-Index of the model 0.840   0.749   0.741  
  1. Abbreviations: ccRCC clear cell renal cell carcinoma, CI confidence interval, C-Index concordance index, G histopathological grading according to Fuhrman, HR hazard ratio, pT pathological tumor classification, R surgical margin classification
  2. aThis study group included the two cohorts of non-metastatic (n = 76) and metastatic (n = 30) patients listed in Table 1; for the analysis of recurrence-free survival, data from four patients could not be obtained
  3. bCalculations were performed with categorization criteria as indicated in brackets and p values were obtained by bootstrapping (2000 resamples). piRNAs were dichotomized using their values obtained in ROC analyses at the point of maximal accuracy to discriminate between dead and alive as well as between recurrence and recurrence-free situation. The thresholds corresponded to those used in the Kaplan-Meier analyses in Figs. 2 and 3
  4. cThe multivariate analysis included all variables of the univariate analyses with p values <0.10
  5. dC-indexes [38] were calculated using models either with all variables or only with clinicopathological data without piRNAs
  6. eThe multivariate analysis with the backward elimination approach was made with p = 0.05 for entry and p = 0.10 for removal. The 95 % CI of the hazard ratios and the p values of the final model were obtained after bootstrapping