Prognostic Significance of Diffusion-Weighted Imaging in T-Staging of Rectal Cancer and Its Association with 18F-FDG PET/CT Parameters
Abstract
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, in-cluding 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 × 10⁻⁶ 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 nonin-vasive prognostic biomarker in non-mucinous rectal adenocarcinoma. Although TLG correlated with T stage, PET/CT-de-rived metabolic parameters did not predict survival. These findings support the potential role of DWI in pre-treatment risk stratification.
Keywords
Apparent diffusion coefficient, total lesion glycolysis, survival analysis, rectal cancer
Supporting Institution
No funding was used in the study.
Ethical Statement
This study was approved by the Non-Interventional Clinical Trials Eth-ics Committee of Sivas Cumhuriyet University on 18.01.2024 with deci-sion number 2024-01/03.
Thanks
None to declare.
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