Multi-Sequence MRI Based Radiomics Nomogram for Prediction Expression of Programmed Death Ligand 1 in Thymic Epithelial Tumor

Abstract Immunotherapy is increasingly being utilized in the management of thymic epithelial tumors (TET). High expression levels of programmed death receptor 1 (PD-1) and its ligand 1 (PD-L1) have been observed in TET, suggesting their potential as prognostic indicators for disease progression and the effectiveness of immunotherapy in TET. We propose that the utilization of quantitative imaging biomarkers could potentially serve as an alternative surrogate for predicting the PD-L1 expression status in clinical decision-making assistance. A total of 124 patients with pathologically confirmed TET (57 PD-L1 positive, 67 PD-L1 negative) were retrospectively enrolled and allocated into training and validation cohorts in a ratio of 7:3. Radiomics features were extracted from T1-weighted, T2-weighted fat suppression, and apparent diffusion coefficient (ADC) map images to establish a radiomics signature in the training cohort. Multivariate logistic regression analysis was conducted to develop a combined radiomics nomogram that incorporated clinical, conventional MR features, or ADC model for evaluation purposes. The performance of each model was compared using receiver operating characteristics analysis, while discrimination, calibration, and clinical efficiency of the combined radiomics nomogram were assessed. The radiomics signature, consisting of four features, demonstrated a favorable ability to predict and differentiate between PD-L1 positive and negative TET patients. The combined radiomics nomogram, which incorporates the peri-cardial invasion sign, ADC value, WHO classification, and radiomics signature, showed excellent performance (training cohort: area under the curve [AUC] = 0.903; validation cohorts: AUC = 0.894). The calibration curve and decision curve analysis further confirmed the clinical usefulness of this combined model. The decision curve analysis demonstrated the clinical utility of the integrated radiomics nomogram. The radiomics signature serves as a valuable tool for predicting the PD-L1 status of TET patients. Furthermore, the integration of radiomics nomogram enhances the personalized prediction capability.