Irfan ATIK, Zekiye HASBEK, Mukaddes YILMAZ, Mehmet ATALAR, Enes GUL, Ramazan Oguz YÜCEER
Archives of Current Medical Research - 2026;7(2):393-400
Background: This study aimed to investigate the relationship between the apparent diffusion coefficient (ADC) derived from diffusion-weighted imaging (DWI) and metabolic parameters obtained from 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) across different T-stages in patients with rectal cancer (RC), and to evaluate the prognostic significance of these imaging biomarkers for survival outcomes. Methods: This retrospective study included patients with non-mucinous rectal adenocarcinoma who underwent both pelvic magnetic resonance imaging (MRI) and 18F-FDG PET/CT before treatment. T-staging was performed using T2-weighted magnetic resonance imaging images, and ADC measurements were obtained from DWI. Metabolic tumor parameters, including maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG), were obtained from PET/CT images. A correlation analysis was performed between ADC and 18F-FDG PET/CT parameters and the T-stage. ROC curve analysis was performed to evaluate the diagnostic performance of ADC and 18F-FDG PET/CT parameters in the early T stage. Overall survival (OS) and progression-free survival (PFS) were estimated and analyzed. Results: A moderate negative correlation was found between T-stage and ADC (r = -0.43, p = 0.003), and a low-moderate positive correlation was found between TLG and ADC (r = 0.33, p = 0.027). ADC showed good diagnostic performance in identifying early T-stage tumors (AUC = 0.86; cutoff = 864 x 10?? mm²/s). The OS in the low ADC group was 58.1+/-6.5 (45.3-70.9) and in the high ADC group 97.4+/-10.9 (76.1-110.8). PFS was 53.7+/-5.9 (42.1-65.1) in the low ADC group and 93.3+/-10.4 (73.0-113.6) in the high ADC group. OS (p = 0.018) and PFS (p = 0.042) were longer in the high ADC group, indicating a statistically significant association. Conclusion: ADC showed a significant association with both tumor stage and survival outcomes and may serve as a noninvasive prognostic biomarker in non-mucinous rectal adenocarcinoma. Although TLG correlated with T stage, PET/CT-derived metabolic parameters did not predict survival. These findings support the potential role of DWI in pre-treatment risk stratification.
