Investigating the potential association between the continuous-time random-walk MR diffusion model and lymph node metastasis and vascular invasion in patients with rectal cancer: A preliminary exploratory study

OBJECTIVES: To explore, as a preliminary study, the quantitative parameters of single-index and continuous-time random-walk (CTRW) magnetic resonance (MR) diffusion models and their association with lymph node metastasis, vascular invasion, and some prognostic factors in patients with rectal cancer. METHODS: This retrospective, exploratory study included a total of 43 patients who were pathologically diagnosed with rectal cancer and underwent preoperative MRI between February 2022 and November 2023. The data were fitted using the single-index and CTRW diffusion models to derive ADC, Dm, α, and β parameters. Differences in quantitative diffusion parameters were assessed for lymph node metastasis, vascular invasion, and p53 status using t-tests and rank-sum tests. The associations of quantitative diffusion parameters with lymph node metastasis and vascular invasion were evaluated using receiver operating characteristic (ROC) analysis. RESULTS: Lymph node metastasis was positive in 25 patients and negative in 18 patients; vascular invasion was positive in 30 patients and negative in 13 patients. In this initial investigation, the Dm and β values derived from the CTRW model showed a certain association with lymph node metastasis (AUCs of 0.76 and 0.76, respectively). Regarding vascular invasion, only the Dm value showed a certain association (AUC of 0.76), while the β value did not demonstrate a significant association after adjustment.The combination of Dm and β demonstrated stronger associations, with AUCs of 0.83 and 0.83, respectively. CONCLUSION: In this exploratory study, the diffusion parameters derived from the CTRW model may be associated with lymph node metastasis and vascular invasion in rectal cancer, but this requires external validation.