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Investigation of the support vector machine algorithm to predict lung radiation‐induced pneumonitis

2007; Wiley; Volume: 34; Issue: 10 Linguagem: Inglês

10.1118/1.2776669

2473-4209

Shifeng Chen, S. Zhou, F Yin, Lawrence B. Marks, Shiva K. Das,

Radiation Effects and Dosimetry

The purpose of this study is to build and test a support vector machine (SVM) model to predict for the occurrence of lung radiation‐induced Grade 2+ pneumonitis. SVM is a sophisticated statistical technique capable of separating the two categories of patients (with/without pneumonitis) using a boundary defined by a complex hypersurface. Despite the complexity, the SVM boundary is only minimally influenced by outliers that are difficult to separate. By contrast, the simple hyperplane boundary computed by the more commonly used and related linear discriminant analysis method is heavily influenced by outliers. Two SVM models were built using data from 219 patients with lung cancer treated using radiotherapy (34 diagnosed with pneumonitis). One model selected input features from all dose and non‐dose factors. For comparison, the other model selected input features only from lung dose‐volume factors. Model predictive ability was evaluated using ten‐fold cross‐validation and receiver operating characteristics (ROC) analysis. For the model , the area under the cross‐validated ROC curve was 0.76 . Compared to the corresponding area of 0.71 , the predictive ability of was improved, indicating that non‐dose features are important contributors to separating patients with and without pneumonitis. Among the input features selected by model , the two with highest importance for predicting lung pneumonitis were: (a) generalized equivalent uniform doses close to the mean lung dose, and (b) chemotherapy prior to radiotherapy. The model is publicly available via internet access.