Delta radiomics for predicting early radiation-induced lung injury after thoracic radiotherapy: a retrospective paired-CT study.

purposeEarly radiation-induced lung injury remains a clinically relevant complication after thoracic radiotherapy. We compared pretreatment, posttreatment, delta radiomics, and combined models based on paired CT scans for early prediction of lung injury.

methodsThis retrospective study included 82 patients with paired CT scans acquired before and after thoracic radiotherapy. The cohort was divided into a training set (n = 57) and an independent test set (n = 25). The endpoint was grade 1 or higher radiation-induced lung injury within 3 months after radiotherapy according to Common Terminology Criteria for Adverse Events Version 5.0 (CTCAE V5.0). Delta radiomics features were defined as posttreatment minus pretreatment values. Five signatures were constructed: clinical, pre, post, delta, and combined. Model performance was evaluated using the area under the receiver operating characteristic curve (AUC), calibration analysis, DeLong testing, and decision curve analysis (DCA).

resultsOnly nodal (N) classification remained significant in multivariable analysis (OR 1.189, 95% CI 1.044-1.354, P = 0.030). In the test cohort, the post signature outperformed the pre signature (AUC 0.844 vs. 0.681). The delta signature achieved the best performance among the radiomics-only models, with a test AUC of 0.882, accuracy of 0.840, sensitivity of 0.889, and specificity of 0.812. The combined signature achieved the highest overall test AUC at 0.889, but the gain over the delta model was limited.

conclusionPosttreatment and delta radiomics outperformed pretreatment radiomics for predicting early radiation-induced lung injury after thoracic radiotherapy. The temporal imaging change captured by paired CT may provide the most informative signal for early risk stratification.