Apparent diffusion coefficients of resectable rectal adenocarcinoma and distal paracancerous tissues derived from diffusion weighted imaging: association with tumor stage

Abstract Purpose To determine whether the apparent diffusion coefficient (ADC) parameters of tumor and distal paracancerous tissues in rectal adenocarcinoma (RA) derived from diffusion weighted imaging (DWI) can be associated with the tumor stages. Materials and methods 134 consecutive patients with RA underwent preoperative DWI (b = 0, 1000 s/mm²). ADC values of the tumor, distal tumor-adjacent and tumor-distant tissues were measured (recorded as ADCt, ADCdta and ADCdtd, respectively). Additionally, ratios of ADCt to ADCdta (ADCt/dta), ADCt to ADCdtd (ADCt/dtd), and ADCdta to ADCdtd (ADCdta/dtd) were calculated. Student’s t-test or Mann-Whitney U test were performed to compare the differences in the aforementioned ADC parameters between different tumor stages. The diagnostic efficacy of individual ADC and combined ADC parameters was evaluated using logistic regression analysis and receiver operating characteristic (ROC) analysis to predict tumor stages. Results Tumors with pT₃–₄ stage demonstrated significantly lower values of ADCt, ADCt/dta, and ADCt/dtd compared to those with pT₁–₂ stage; tumors with pN₁–₂ stage exhibited significantly lower values of ADCt and ADCt/dta compared to those with pN₀ stage; and cases with lymph node metastasis (LNM) showed significantly lower values of ADCt, ADCt/dta, and ADCt/dtd compared to those without LNM (all P-values < 0.05). Area under the ROC curves (AUC) of the combination involving ADCt and ADCt/dta was higher than that of individual ADC parameters when assessing pT stage, pN stage, and LNM. Conclusion The ADC parameters of tumor and distal paracancerous tissues could be somewhat helpful in preoperatively assessing pT stage, pN stage, and LNM in RA.