Delta-radiomics Approach Using Contrast-enhanced and Non-contrast-enhanced Computed Tomography Images for Predicting Distant Metastasis in Patients with Borderline Resectable Pancreatic Carcinoma

Abstract

PurposeTo predict distant metastasis (DM) in patients with borderline resectable pancreatic carcinoma (BRPC) using delta-radiomics features calculated from contrast-enhanced computed tomography (CECT) and non-CECT images. MethodsAmong 250 patients who underwent radiotherapy at our institution between February 2013 and December 2021, 67 patients were deemed eligible. A total of 11 clinical features and 3,906 radiomics features were incorporated. Radiomics features were extracted from CECT and non-CECT images and the differences between these features were calculated, resulting in delta-radiomics features. The patients were randomly divided into the training (70%) and test (30%) datasets for model development and validation. Predictive models were developed with clinical features (clinical model), radiomics features (radiomics model), and a combination of the abovementioned features (hybrid model) using Fine–Gray regression (FG) and random survival forest (RSF). Optimal hyperparameters were determined using stratified five-fold cross-validation. Subsequently, the developed models were applied to the remaining test datasets, and the patients were divided into the high- or low-risk groups based on their risk scores. Prognostic power was assessed using the concordance index (C-index) with 95% confidence intervals obtained through 2,000 bootstrapping iterations. Statistical significance between the two groups was assessed using Gray's test. ResultsAt a median follow-up period of 23.8 months, 47 (70.1%) patients developed DM. The C-indices of the FG-based clinical, radiomics, and hybrid models were 0.548, 0.603, and 0.623, respectively, in the test dataset, whereas those of the RSF-based models were 0.598, 0.680, and 0.727, respectively. The RSF-based model, including delta-radiomics features, significantly divided the cumulative incidence curves into two groups (P<0.05). The feature map of the gray-level size-zone matrix showed that the difference in feature values between CECT and non-CECT images correlated with the incidence of DM. ConclusionsDelta-radiomics features obtained from CECT and non-CECT images using RSF successfully predict the incidence of DM in patients with BRPC.