To explore the predictive value of quantitative parameters of diffusion- weighted imaging (DWI) combined with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for pathological complete response (pCR) in patients with locally advanced rectal cancer (LARC) after neoadjuvant therapy.

A retrospective analysis was conducted on the medical records of 120 patients with LARC admitted to Xidian Group Hospital from January 2022 to January 2025, tumor regression grade (TRG) was adopted, TRG grade 0 was defined as the pCR group (n=38), and the rest were defined as the non-PCR group (n=82). The quantitative parameters of apparent diffusion coefficient (ADC), transport constant (Ktrans), percentage of extracellular space volume outside the blood vessels (Ve), and rate constant (Kep) before and after neoadjuvant therapy were compared between the two groups. Spearman correlation analysis was used to analyze the correlation between quantitative parameters of DWI and DCE-MRI and pCR after neoadjuvant therapy for LARC. ROC curve was used to analyze the predictive value of DWI combined with quantitative parameters of DCE-MRI before treatment for pCR after neoadjuvant therapy for LARC.

After treatment, the ADC of patients in the pCR group was higher than that in the non-pCR group, while Kep, Ve and Ktran were all lower than those in the non-pCR group (P<0.05). The results of Spearman correlation analysis showed that ADC before treatment was positively correlated with pCR after neoadjuvant therapy for LARC, while Kep, Ve, and Ktrans were all negatively correlated with pCR after neoadjuvant therapy for LARC (P<0.05). ROC curve analysis indicated that the areas under the curve (AUC) of ADC, Kep, Ve, Ktrans and their combined detections before treatment for predicting pCR after neoadjuvant therapy for LARC were 0.667, 0.511, 0.797, 0.666 and 0.880, respectively. The sensitivities were 76.32%, 78.95%, 68.42%, 73.68%, and 81.58% respectively, and the specificities were 75.61%, 78.05%, 70.73%, 72.07%, and 86.59% respectively. Before treatment, the AUC of ADC, Kep, Ve, and Ktrans was the largest, and their sensitivity and specificity were also the highest (P<0.05).

The quantitative parameters of DWI combined with DCE-MRI can effectively predict pCR in patients with LARC after neoadjuvant therapy, and the combined detection can improve the predictive efficacy.