Nomograms to Predict the Disease-free Survival and Overall Survival after Radiofrequency Ablation for Hepatocellular Carcinoma

Abstract

Objective The purpose of this study was to construct nomograms for the disease-free survival (DFS) and overall survival (OS) of post-radiofrequency ablation (RFA) patients with hepatocellular carcinoma (HCC). Furthermore, we compared the prognostic predictive ability of these nomograms for estimating per-patient outcomes with that of traditional staging systems. Methods We retrospectively enrolled 298 patients in the training set and 272 patients in the validation set who underwent RFA for HCC. The nomograms for the DFS and OS were constructed from the training set using the multivariate Cox proportional hazards model. The discriminatory accuracy of the models was compared with traditional staging systems by analyzing the Harrell's C-index. Results The DFS nomogram was developed based on the tumor size, tumor number, aspartate aminotransferase (AST), albumin, age, and α-fetoprotein. The OS nomogram was developed based on the tumor size, the model for end-stage liver disease, AST, and albumin. Our DFS and OS nomograms had good calibration and discriminatory abilities in the training set, with C-indexes of 0.640 and 0.692, respectively, that were greater than those of traditional staging systems. The C-indexes of our DFS and OS nomograms were also greater than those of traditional staging systems in the validation set, with C-indexes of 0.614 and 0.657, respectively. RFA patients were stratified into low- and high-risk groups based on the median nomogram scores. High-risk patients receiving surgical resection (SR) were associated with a better DFS and OS than those undergoing RFA. However, the DFS and OS were similar between the low-risk RFA and SR groups. Conclusion We constructed reliable and useful nomograms that accurately predict the DFS and OS after RFA for early-stage HCC patients. These graphical tools are easy to use and will assist physicians during the therapeutic decision-making process.

Keywords: disease-free survival; hepatocellular carcinoma; nomogram; overall survival; radiofrequency ablation.

Figure 1.

Cumulative DFS (A) and OS (B) curves of the two series of patients included in the study. The solid line represents the training set, and the dotted line represents the validation set. DFS: disease-free survival, OS: overall survival

Figure 2.

Nomogram for predicting (A) the disease-free survival and (B) the overall survival of HCC patients following RFA. HCC: hepatocellular carcinoma, RFA: radiofrequency ablation

Figure 3.

Kaplan-Meier curves demonstrating (A) the disease-free survival and (B) the overall survival for HCC patients following RFA according to the quartiles of the predicted disease-free or overall survival. HCC: hepatocellular carcinoma, RFA: radiofrequency ablation

Figure 4.

Calibration curves for the nomogram-predicted probability of the 1- (A), 3- (B), and 5- (C) year DFS and the nomogram-predicted probability of the 3- (D), 5- (E), and 7- (F) year OS in the training set. Curves for a hypothetical ideal nomogram are represented by dashed lines, and those for the current nomogram are represented by solid lines. Vertical bars indicate 95% confidence intervals. DFS: disease-free survival, OS: overall survival

Figure 5.

Calibration curves for the nomogram-predicted probability of the 1- (A), 3- (B), and 5- (C) year DFS and the nomogram-predicted probability of the 3- (D), 5- (E), and 7- (F) year OS in the validation set. Curves for a hypothetical ideal nomogram are represented by dashed lines, and those for the current nomogram are represented by solid lines. Vertical bars indicate 95% confidence intervals. DFS: disease-free survival, OS: overall survival

Figure 6.

The DFS and OS in similar-stage HCC (≤ 3 tumors each ≤ 3 cm in diameter) patients receiving SR or RFA in the training set. (A) Patients undergoing SR had a better DFS than high-risk patients receiving RFA (p=0.0331). (B) The DFS was similar between the low-risk RFA and SR groups (p=0.184). (C) SR patients had a better OS than high-risk RFA patients (p=0.0004). (D) The OS was similar between the low-risk RFA and SR groups (p=0.165). DFS: disease-free survival, OS: overall survival, HCC: hepatocellular carcinoma, SR: surgical resection, RFA: radiofrequency ablation

Figure 7.

The DFS and OS in similar-stage HCC (≤ 3 tumors each ≤ 3 cm in diameter) patients receiving SR or RFA in the validation set. (A) Patients undergoing SR had a better DFS than high-risk patients receiving RFA (p=0.0473). (B) The DFS was similar between the low-risk RFA and SR groups (p=0.141). (C) SR patients had a better OS than high-risk RFA patients (p=0.0148). (D) The OS was similar between the low-risk RFA and SR groups (p=0.625). DFS: disease-free survival, OS: overall survival, HCC: hepatocellular carcinoma, SR: surgical resection, RFA: radiofrequency ablation