Exploratory radiomic features from integrated ${}^{18}$F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging are associated with contemporaneous metastases in oesophageal/gastroesophageal cancer

The purpose of this study was to determine if ${}^{18}$F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (${}^{18}$F-FDG PET/MRI) features are associated with contemporaneous metastases in patients with oesophageal/gastroesophageal cancer. Following IRB approval and informed consent, patients underwent a staging PET/MRI following ${}^{18}$F-FDG injection (326 ± 28 MBq) and 156 ± 23 min uptake time. First-order histogram and second-order grey level co-occurrence matrix features were computed for PET standardized uptake value (SUV) and MRI T1-W, T2-W, diffusion weighted (DWI) and apparent diffusion coefficient (ADC) images for the whole tumour volume. K-means clustering assessed the correlation of feature-pairs with metastases. Multivariate analysis of variance (MANOVA) was performed to assess the statistical separability of the groups identified by feature-pairs. Sensitivity (SN), specificity (SP), positive predictive value (PPV), negative predictive value (NPV), and accuracy (ACC) were calculated for these features and compared with SUV${}_{max}$, ADC${}_{mean}$ and maximum diameter alone for predicting contemporaneous metastases. Twenty patients (18 males, 2 female; median 67 years, range 52–86) comprised the final study cohort; ten patients had metastases. Lower second-order SUV entropy combined with higher second-order ADC entropy were the best feature-pair for discriminating metastatic patients, MANOVA p value <0.001 (SN = 80%, SP = 80%, PPV = 80%, NPV = 80%, ACC = 80%). SUV${}_{max}$ (SN = 30%, SP = 80%, PPV = 60%, NPV = 53%, ACC = 55%), ADC${}_{mean}$ (SN = 20%, SP = 70%, PPV = 40%, NPV = 47%, ACC = 45%) and tumour maximum diameter (SN = 10%, SP = 90%, PPV = 50%, NPV = 50%, ACC = 50%) had poorer sensitivity and accuracy. High ADC entropy combined with low SUV entropy is associated with a higher prevalence of metastases and a promising initial signature for future study.