What does this research mean for the field?

The apparent diffusion coefficient (ADC) derived from diffusion-weighted imaging is a significant noninvasive prognostic biomarker for tumor stage and survival in non-mucinous rectal adenocarcinoma, whereas PET/CT-derived metabolic parameters do not predict survival. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

This research examines the correlation between ADC from diffusion-weighted imaging and metabolic parameters from 18F-FDG PET/CT in rectal cancer patients.

June 3, 2026

Prognostic Significance of Diffusion-Weighted Imaging in T-Staging of Rectal Cancer and Its Association with 18F-FDG PET/CT Parameters

Key Points

This research examines the correlation between ADC from diffusion-weighted imaging and metabolic parameters from 18F-FDG PET/CT in rectal cancer patients.
Retrospective study of patients with non-mucinous rectal adenocarcinoma undergoing MRI and PET/CT.
T-staging performed via T2-weighted MRI; ADC measured from DWI; metabolic parameters obtained from PET/CT.
Correlation analysis and ROC curve analysis were conducted to evaluate diagnostic performance and survival outcomes.
Moderate negative correlation between T-stage and ADC (r = -0.43, p = 0.003); low-moderate positive correlation between TLG and ADC (r = 0.33, p = 0.027).
ADC showed good diagnostic performance for early T-stage tumors (AUC = 0.86; cutoff = 864 × 10⁻⁶ mm²/s).
Overall survival in low ADC group: 58.1 months; high ADC group: 97.4 months (p = 0.018); PFS: low ADC 53.7 months, high ADC 93.3 months (p = 0.042).

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.

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