In the present study, it is the first work predicting the recurrence risk of IAs with ML models. We developed five ML models using 7 variables to predict recurrence of patients with IAs after EVT in 6 months and GBDT model showed the best prediction performance. In addition, two interpretation algorithms were introduced to explain the GBDT model. The significance of our study in clinical practice is that we provide an effective tool for deciding on individual intervention strategies in patients with IAs.
ML models make our study more close-linked to the clinical setting, and have a broader application prospects. ML models have advantages in handling variables with non-linear relationship, interaction, and missing values. Besides, ML models generate an individualized probability of outcome for a patient, which is different from traditional scoring system. As the technology matures, ML algorithms can be integrated into decision-making systems which can process large amounts of data automatically. The decision-making system is helpful to make clinical judgments and to provide patients with individual treatment. Furthermore, electronic patient record (EPR) system makes it convenient to the application of ML models.
As a popular ensemble method, GBDT algorithm has been successfully applied in medical fields[6] because of favorable discrimination performance and ability to capture complex relationships[29]. Among the five ML models in our study, GBDT model displayed best discriminatory ability (AUC, 0.842; 95% CL, 0.790–0.895), which suggested that it is a powerful model for predicting recurrence of patients with IAs in 6 months. GBDT model has a sensitivity of 81.5%, which means only 18.5% of aneurysms with recurrence are not identified correctly. From clinical perspective, unnecessary intervention for non-recurrent aneurysm is acceptable, but it will cause serious consequences if recurrent aneurysms cannot be correctly predicted. Thus, it is more valuable to identify IAs with recurrence than IAs without recurrence. That is to say, sensitivity is more important than specificity in our ML models. Our GBDT model with best AUC and sensitivity among five models contributes to predict the recurrence risk of IAs.
An ADASYN sampling method was used to tackle the issue of class imbalance in our study. Among 425 cases of IAs treated with EVT, 66 cases recurred postoperatively, with a total recurrence rate of 15.5%, which was consistent with the results of previous studies[11, 24]. Thus, there was a significant sample imbalance between recurrence group and non-recurrence group. Obviously, misclassification of IAs with recurrence (minority class) will lead to more serious costs than IAs without recurrence (majority class), that’s why the identification of IAs with recurrence (minority class cases) is of greater need in medical diagnosis. Assuming that all the cases are classified into the majority class, the overall accuracy of the model is still high, but it is a false reliable model actually. Due to the above assumption, we adopted ADASYN sampling approach to generate more synthetic data for IAs with recurrence (minority class cases), which has been introduced in previous studies[13]. This kind of sampling technique can reduce the bias due to class imbalance by changing the data distribution. Therefore, our GBDT model which considering class imbalance has a reliable performance to identify IAs with high risk of recurrence.
Another significant advantage of our GBDT model is its visualization and interpretability. ML models for clinical applications have a fatal drawback that the relationship between clinical factors and reactions is invisible to doctors. However, it is impossible for doctors to trust a ML diagnosis without a reasonable explanation. LIME algorithm explains the prediction of ML models in an interpretable manner, and LIME algorithm was applied to investigate feature contributions for individual instances. In previous ML models for clinical predictions, researchers usually used feature importance to explain the contribution of each feature to the prediction capability of the model. compared with conventional feature importance, SHAP determines whether the influence of a feature is positive or negative. Therefore, we Introduced LIME and SHAP algorithms to explain the recurrence prediction of ML models. The above two algorithms can greatly increase the clinicians' trust in the model and experts can provide knowledge-based validation for the interpretation of ML model.
In our study, several predictors of recurrence in patients with IAs have been established. On the one hand, Longest diameter of the aneurysm, Raymond grade and wide-necked aneurysms have been confirmed as risk factors, which is consistent with previous studies[17, 19, 24, 28]. Our study also confirms that stent-assisted coil (SAC) embolization is associated with lower recurrence compared with simple conventional coil, and this finding was also reported by previous studies[22, 28]. On the other hand, Our results indicated that ruptured aneurysms related to lower recurrence rate in SHAP analysis, which is consistent with that of Peluso (2008) who found ruptured aneurysms associated with lower re-treatment rates[20]. This finding may be due to the larger size of unruptured aneurysms in our study. In addition, our found that history of hypertension was an independent predictor of recurrence. Previous studies have reported that hypertension remains a risk factor in the steady prognosis of IAs after EVT[14, 21]. Biological evidence shows that that abnormal hemodynamic status are related to vascular remodeling and the generation of aneurysms, particularly, self-hypertension often contributes to the development and enlargement of aneurysms[16]. However, a previous study indicated that hypertension was not a predictor of recurrence[15]. Although further research on hypertension and recurrence has to be implemented, our study strongly suggests that blood pressure should be effectively monitored in the postoperative stage. In addition, smoking is also a known risk factor for aneurysm development and aneurysmal subarachnoid hemorrhage[10]. But the relationship between smoking and aneurysm recurrence was still controversial [1, 7]. Our study found that smoking was not significantly associated with aneurysm recurrence.
Our study also has some limitations. First, patients with IAs were selected from a single hospital and no external validation was performed, the generalizability performance of the ML models merits investigation in patients treated at other institutions and by other neurologists. Second, several patients potentially eligible for our study could not be contacted and the cases were excluded. Thus, it is unclear whether we have overestimated or underestimated the risk of recurrence. Finally, data of possible hemodynamic predictors of recurrence such as flow momentum[4] were not available in our study. Future prospective studies will have to assess whether incorporating novel predictors may improve the performance of predictive model.