Clinical value of intratumoral and peritumoral CT radiomics models for discriminating benign and malignant parotid gland tumors.

Objective: To evaluate the utility of combining unenhanced and contrast-enhanced CT intratumoral and peritumoral radiomic features with clinical variables for distinguishing benign from malignant parotid gland tumors. Methods: We retrospectively collected clinical and imaging data from 171 patients with pathologically confirmed parotid gland tumors treated at Baoding First Central Hospital between June 2019 and June 2025 (101 benign, 70 malignant). Tumor ROIs were manually delineated slice-by-slice on non-contrast, arterial-phase and venous-phase CT images, and peritumoral regions were automatically expanded by 1-4 mm. The cohort was randomly split into training and test sets at a 7:3 ratio. After extraction and selection of radiomic features, multiple models were constructed for intratumoral, various peritumoral ranges (1-4 mm) and intratumoral+peritumoral combinations. Model performance was evaluated by ROC curves, the optimal radiomics model was selected and integrated with the clinical model to produce a combined model, and a nomogram was subsequently developed. Results: The AUC values of the intratumoral, peritumoral (1-4 mm) and intratumoral+peritumoral models in the training set were 0.966, 0.953, 0.927, 0.983, 0.947, 0.959, 0.956, 0.909 and 0.976, respectively; in the test set the AUCs were 0.797, 0.766, 0.791, 0.714, 0.710, 0.805, 0.836, 0.778 and 0.753, respectively. According to the DeLong test, in the training set the differences between intratumor+peritumor 3mm Conclusion: A multiphase CT radiomics approach that fuses intratumoral features with a 2 mm peritumoral zone robustly distinguishes benign from malignant parotid gland tumors. Integration with key clinical predictors further enhances diagnostic accuracy, supporting clinical translation of the combined model for noninvasive tumor characterization.