A sample model established by S-index predicting overall survival after curative resection of primary hepatocellular carcinoma

Abstract

Purpose: Prognostic prediction after curative resection of primary hepatocellular carcinoma (PHCC) remains an arduous task. The S-index calculated from γ-glutamyl transpeptidase, albumin, and platelets is reported to predict the severity of liver fibrosis. We constructed a nomogram for predicting the survival probability of PHCC based on a new indicator, the S-index, combined with other routine clinical parameters.

Patients and methods: We selected 490 patients with PHCC postradical surgery at the First Affiliated Hospital of Wenzhou Medical University between January 2007 and January 2014. The subjects were randomly allocated into the training cohort and the validation cohort in the ratio 7:3 by the digital method. Important variables screened by univariate analysis were included in multivariate analysis to obtain independent risk factors for predicting the prognosis of PHCC. The construction of the nomogram was based on Cox proportional hazard regression models. The concordance index (C-index) was used in the nomogram for evaluating the model performance for prognosis. We drew time-dependent receiver operating characteristic curves to compare our model with other staging systems.

Results: The nomogram based on six independent risk factors after multivariate analyses had good predictive power after radical surgery of PHCC. In the training and validation groups, the C-index of the nomogram was highly consistent for evaluating survival from PHCC. Compared with the traditional scoring system, the areas under time-dependent receiver operating characteristic curves were 0.7382, 0.7293, and 0.7520 for 1-, 3-, and 5-year overall survival, respectively. In summary, the nomogram showed excellent results in terms of prognosis of PHCC.

Conclusion: Based on the S-index and the other clinical indicators, we developed a precise nomogram that predicts the survival probability of patients with PHCC after radical surgery. This tool can provide effective information for surgeons and patients.

Keywords: PHCC; nomogram; prognosis; radical resection.

Figure 1

Nomogram for predicting overall survival after curative resection of PHCC. Notes: To obtain the corresponding survival probability, sum up each variable score and draw a vertical line from the total points scale to the survival rate scale. Abbreviations: ALB, albumin; PHCC, primary hepatocellular carcinoma; PVTT, portal vein tumor thrombus; TBil, total bilirubin.

Figure 2

Calibration curves for predicting overall survival probability by the nomogram in the training and validation sets. Notes: Calibration curves of the prognostic nomogram for 1-year overall survival (A), 3-year overall survival (B) and 5-year overall survival (C) in the training set, correspondingly, calibration curves for 1-year overall survival (D), 3-year overall survival (E), and 5-year overall survival (F) in the validation set.

Figure 3

The tdROC curve of the prognostic nomogram, S-index, CLIP, BCLC and Okuda score in the training cohort. Note: The tdROC curve for 1-year survival (A), 3-year survival (B), and 5-year survival (C). Abbreviations: BCLC, Barcelona Clinic Liver Cancer; CLIP, Cancer of the Liver Italian Program; tdROC, time-dependent receiver operating characteristic.

Figure 4

Survival curves stratified by the score calculated by the nomogram in the training cohort (low risk: <200; intermediate risk: 200–250; and high risk: >250).