Objective To investigate the establishment and application value of a radio-mics prediction model for lymph node metastasis of gallbladder carcinoma based on dual-phase enhanced computed tomography (CT).

Methods The retrospective cohort study was conducted. The clinicopathological data of 194 patients with gallbladder carcinoma who were admitted to the First Affiliated Hospital of Xi'an Jiaotong University from January 2012 to December 2020 were collected. There were 70 males and 124 females, aged (64±10)years. All patients underwent curative-intent resection of gallbladder carcinoma. A total of 194 patients were randomly divided into 156 cases in training set and 38 cases in test set according to the ratio of 8:2 based on random number method in R software. The training set was used to establish a diagnostic model, and the test set was used to validate the diagnostic model. After the patients undergoing CT examination, image analysis was performed, radiomics features were extracted, and a radiomics model was established. Based on clinicopathological data, a nomogram prediction model was established. Observation indicators: (1) lymph node dissection and histopathological examination results; (2) establishment and characteristic analysis of a radiomics prediction model; (3) analysis of influencing factors for lymph node metastasis of gallbladder carcinoma; (4) establishment of a nomogram prediction model for lymph node metastasis; (5) comparison of the predictive ability between the radiomics prediction model and nomogram prediction model for lymph node metastasis. Measurement data with normal distribution were represented as Mean±SD, and measurement data with skewed distribution were represented as M(range). Count data were expressed as absolute numbers, and comparison between groups was performed by the chi-square test. Univariate analysis was conducted by the chi-square test, and multivariate analysis was performed by the Logistic regression model forward method. The receiver operating characteristic curve was drawn, and the area under curve, decision curve, confusion matrix were used to evaluate the predictive ability of prediction models.

Results (1) Lymph node dissection and histopathological examination results. Of the 194 patients, 182 cases underwent lymph node dissection, with the number of lymph node dissected as 8(range, 1‒34) per person and the number of positive lymph node as 0(range, 0‒11) per person. Postoperative histopathological examination results of 194 patients: 122 patients were in stage N0, with the number of lymph node dissected as 7(range, 0‒27) per person, 48 patients were in stage N1, with the number of lymph node dissected as 8(range, 2‒34) per person and the number of positive lymph node as 1(range, 1‒3) per person, 24 patients were in stage N2, with the number of lymph node dissected as 11(range, 2‒20) per person and the number of positive lymph node as 5(range, 4‒11) per person. (2) Establishment and characteristic analysis of a radiomics prediction model. There were 107 radiomics features extracted from 194 patients, including 18 first-order features, 14 shape features and 75 texture features. According to the intra-group correlation coefficient and absolute median difference of each radiomics feature, mutual information, Select K-Best, least absolute shrinkage and selection operator regression were conducted to further reduce dimensionality. By further combining 5 different machine learning algorithms including random forest, gradient boosting secession tree, support vector machine (SVM), K-Nearest Neighbors and Logistic regression, the result showed that the Select K-Best_SVM model had the best predictive performance after analysis, with the area under receiver operating characteristic curve as 0.76 in the test set. (3) Analysis of influencing factors for lymph node metastasis of gallbladder carcinoma. Results of univariate analysis showed that systemic inflammation response index, carcinoembryonic antigen (CEA), CA19-9, CA125, radiological T staging and radiological lymph node status were related factors for lymph node metastasis of patients with gallbladder cancer (χ²=4.20, 11.39, 5.68, 11.79, 10.83, 18.58, P<0.05). Results of multivariate analysis showed that carcinoembryonic antigen, CA125, radiological T staging (stage T3 versus stage T1‒2, stage T4 versus stage T1‒2), radiological lymph node status were independent influencing factors for lymph node metastasis of patients with gallbladder carcinoma hazard ratio=2.79, 4.41, 5.62, 5.84, 3.99, 95% confidence interval (CI) as 1.20‒6.47, 1.81‒10.74, 1.50‒21.01, 1.02‒33.31, 1.87‒8.55, P<0.05. (4) Establishment of a nomogram prediction model for lymph node metastasis. A nomogram prediction model was established based on the 4 independent influencing factors for lymph node metastasis of gallbladder carcinoma, including CEA, CA125, radiological T staging and radiological lymph node status. The concordance index of the nomogram model was 0.77 (95%CI as 0.75‒0.79) in the training set and 0.73 (95%CI as 0.68‒0.72) in the test set, respectively. (5) Comparison of the predictive ability between the radiomics predic-tion model and nomogram prediction model for lymph node metastasis. The receiver operating characteristic curve showed that the areas under the curve of Select K-Best_SVM radiomics model were 0.75 (95%CI as 0.74‒0.76) in the training set and 0.76 (95%CI as 0.75‒0.78) in the test set, respectively. The areas under the curve of nomogram prediction model were 0.77 (95%CI as 0.76‒0.78) in the training set and 0.70 (95%CI as 0.68‒0.72) in the test set, respectively. The decision curve analysis showed that Select K-Best_SVM radiomics model and nomogram prediction model had a similar ability to predict lymph node metastasis. The confusion matrix showed that Select K-Best_SVM radiomics model had the sensitivity as 64.29% and 75.00%, the specificity as 73.00% and 59.09% in the training set and test set, respectively. The nomogram had the sensitivity as 51.79% and 50.00%, the specificity as 80.00% and 72.27% in the training set and test set, respectively.

Conclusion A dual-phase enhanced CT imaging radiomics prediction model for lymph node metastasis of gallbladder carcinoma is successfully established, and its predictive ability is good and consistent with that of nomogram.