Incorporation of pre‐therapy 18F‐FDG uptake data with CT texture features into a radiomics model for radiation pneumonitis diagnosis

Purpose To determine whether the addition of standardized uptake value (SUV) from PET scans to CT lung texture features could improve a radiomics‐based model of radiation pneumonitis (RP) diagnosis in patients undergoing radiotherapy. Methods and materials Anonymized data from 96 esophageal cancer patients (18 RP‐positive cases of Grade ≥ 2) were collected including pre‐therapy PET/CT scans, pre‐/post‐therapy diagnostic CT scans and RP status. Twenty texture features (first‐order, fractal, Laws’ filter and gray‐level co‐occurrence matrix) were calculated from diagnostic CT scans and compared in anatomically matched regions of the lung. Classifier performance (texture, SUV, or combination) was assessed by calculating the area under the receiver operating characteristic curve (AUC). For each texture feature, logistic regression classifiers consisting of the average change in texture feature value and the pre‐therapy SUV standard deviation (SUVSD) were created and compared with the texture feature as a lone classifier using ANOVA with correction for multiple comparisons (P < 0.0025). Results While clinical parameters (mean lung dose, smoking history, tumor location) were not significantly different among patients with and without symptomatic RP, SUV and texture parameters were significantly associated with RP status. AUC for single‐texture feature classifiers alone ranged from 0.58 to 0.81 and 0.53 to 0.71 in high‐dose (≥ 30 Gy) and low‐dose (< 10 Gy) regions of the lungs, respectively. AUC for SUVSD alone was 0.69 (95% confidence interval: 0.54–0.83). Adding SUVSD into a logistic regression model significantly improved model fit for 18, 14 and 11 texture features and increased the mean AUC across features by 0.08, 0.06, and 0.04 in the low‐, medium‐, and high‐dose regions, respectively. Conclusions Addition of SUVSD to a single‐texture feature improves classifier performance on average, but the improvement is smaller in magnitude when SUVSD is added to an already effective classifier using texture alone. These findings demonstrate the potential for more accurate assessment of RP using information from multiple imaging modalities.