Application of diffusion kurtosis imaging in differentiating T0-T1 from T2 rectal tumors

High-spatial-resolution T2-weighted imaging (HR-T2WI) has been demonstrated to overestimate the staging of early rectal cancer, which could lead to missed opportunities for organ-preserving treatments. This study aimed to investigate the value of diffusion kurtosis imaging (DKI) in distinguishing between T0-T1 and T2 rectal tumors.

A total of 138 patients with pathologically confirmed T0-T2 rectal tumors who underwent surgery between 2018 and 2023 were included. The pathological findings on tumor staging obtained from surgical specimens were used as the reference standard. The depth of tumor invasion was assessed using HR-T2WI. Kurtosis and diffusivity from DKI and apparent diffusion coefficient (ADC) from diffusion-weighted imaging were measured for the entire tumor. Diffusion parameters were compared between pT0-T1 and pT2 tumors. Multivariable logistic regression and receiver operating characteristic curve analyses were conducted to evaluate the diagnostic performance of significant individual parameters and their combinations in determining pT0-T1 tumors.

Kurtosis was lower in pT0-T1 than in pT2 rectal tumors (0.799 vs. 0.950, P < 0.001), while diffusivity and ADC were higher than those of pT2 rectal cancer (1.732 × 10^-3 mm²/s vs. 1.368 × 10^-3 mm²/s, P < 0.001; 1.316 × 10^-3 mm²/s vs. 1.043 × 10^-3 mm²/s, P < 0.001). Diffusivity demonstrated the highest diagnostic efficacy in differentiating pT0-T1 from pT2 rectal tumors, with an AUC of 0.810, which was higher that of HR-T2WI (AUC = 0.752, P < 0.001) and kurtosis (AUC = 0.729, P = 0.007), but showed no difference compared to ADC (AUC = 0.785, P = 0.087). A multivariable logistic regression model incorporating HR-T2WI and diffusivity improved diagnostic performance compared with all other individual parameters, achieving an AUC of 0.885 (all P < 0.05).

The combination of HR-T2WI and diffusivity can effectively detect pT0-T1 rectal tumors. HR-T2WI combined with diffusivity derived from DKI may serve as a potential biomarker for early assessment of rectal tumors, offering valuable insights for selecting suitable candidates for organ-preserving surgery.