In this study, we assessed the prognostic value of 18F-FDG PET/CT radiomics alongside body composition indices and clinicopathological parameters in EC patients. Our findings identified Rad-score, SMI, and VATI as independent predictors of both PFS and OS. Integrating clinicopathological data with imaging-derived parameters, such as radiomics and body composition status, to develop new composite biomarkers yielded superior prognostic outcomes compared to using these factors individually.
Recent literature has seen a surge in publications exploring functional parameters from standard 18F-FDG PET/CT, including metabolic tumor volume (MTV), total lesion glycolysis (TLG), and radiomics, highlighting their significance in prognostic assessments across various cancers [25–29]. Radiomics, which extracts extensive high-dimensional data from medical images, offers the potential to investigate imaging heterogeneity beyond visual perception [30]. For instance, Amrane et al. have retrospectively studied 97 patients with gastroesophageal junction cancer (GEJC) and found that increased histogram entropy of pre-treatment PET-measured tumor correlates with poorer RFS and OS [31]. Similarly, another study has indicated that higher kurtosis in CT and PET components is associated with a worse prognosis in patients with esophagogastric adenocarcinoma [17]. These findings underscore the potential of identifying tumor heterogeneity through imaging data to enhance treatment outcomes. While there are parallels with previous studies, our research uniquely focused on patients with ESCC, contributing to a more homogeneous cohort.
In our study, potential predictors were selected using the LASSO method to construct the Rad-score, which incorporates biologically informative features, including texture features (e.g., GLCM, GLRLM, and GLZLM), conventional features (SUVmean), and three-dimensional shape features. Zhu et al. have identified 16 features associated with distant metastasis in EC patients out of 851 radiomic features, primarily from shape, GLCM, GLSZM, GLDM, and NGTDM categories [32], aligning closely with our findings.
Previous research demonstrates that three-dimensional shape features (e.g., irregularity and sphericity) extracted from PET and low-dose CT images exhibit high reproducibility and accurately reflect lesion morphology [33]. Moreover, these high-dimensional image features enable the quantification of multi-frequency tumor information and show promise in predicting pathologic type, lymph node metastasis, and prognosis [6, 34, 35]. Our study specifically revealed that a higher Rad-score correlated with a poorer prognosis.
As previously noted, body composition parameters have been recognized as predictors in cancer patients [36–38]. In our study, sarcopenia predicted significantly lower PFS (HR = 5.742, 95% CI: 2.349–14.037, P < 0.001) and OS (HR = 4.477, 95% CI: 1.704–11.759, P = 0.002). Additionally, AT plays a crucial role in ESCC; patients with a high VATI had markedly shorter median PFS (HR = 6.663, 95% CI: 2.806–15.821, P < 0.001) and OS (HR = 0.323, 95% CI: 0.111–0.935, P = 0.037) compared to those with lower VATI.
The nomogram integrates multiple high-risk variables into a quantitative model, surpassing traditional tools in predicting disease onset and progression [39, 40]. However, to our knowledge, there is limited literature on predicting prognosis in ESCC using PET/CT imaging parameters and body composition indicators. Our study demonstrated that the multiparametric nomogram model, incorporating stage, LVI, BMI, SMI, VATI, and Rad-score, achieved superior C-index values compared to clinical or combined clinical-body composition index models (PFS: 0.810 vs. 0.666 vs. 0.782; OS: 0.806 vs. 0.661 vs. 0.752).
This study has several limitations. Firstly, it was a retrospective study conducted at a single institution, focusing exclusively on ESCC, with a limited sample size. Secondly, the relatively small cohort size precluded external validation of our findings. Therefore, future research collaborations with external institutions are warranted to validate our results in a larger and more diverse cohort.