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The predictive value of multi-phase contrast-enhanced MRI for pathological complete response after neoadjuvant
Jingjing Xie1, Kaihe Lin1, Suying Wu1
1Department of Radiology, The First Hospital of Putian City, Putian, Fujian, China.
Background:
Accurate prediction of pathological complete response (pCR) after neoadjuvant chemoradiotherapy (NCRT) for rectal cancer is crucial for determining subsequent treatment strategies. Although studies have shown that single-phase contrast-enhanced (CE) imaging can accurately assess complete response status after NCRT, the diagnostic value of different phases in multi-phase CE MRI remains unclear.
Methods:
A retrospective cohort study was conducted involving patients with locally advanced rectal cancer who underwent total mesorectal excision (TME) after NCRT at our institution between August 2020 and October 2025. Two radiologists, blinded to individual, clinical, and histopathological information, independently assessed enhancement characteristics on multi-phase CE MRI. The diagnostic efficacy of each imaging phase for predicting pCR was compared to identify the optimal phase. Multivariate logistic regression analysis was conducted to explore independent predictors of pCR.
Results:
A total of 68 patients (mean age 64.8 ± 8.5 [standard deviation]) were included. The third phase of the CE (CE-3) MRI series (approximately 76 seconds) demonstrated optimal performance in predicting pCR, with an accuracy of 0.882, specificity of 0.925, and an area under the receiver (AUC) of 0.829 (95% CI: 0.708-0.950). Inter-observer agreement was favorable (κ = 0.672, 95% CI: 0.461-0.886). Compared with T2-weighted imaging combined with diffusion-weighted imaging (T2DWI), CE-3 MRI demonstrated superior accuracy in identifying treatment response (0.882 vs 0.647, p=0.002) and a superior ability to identify patients with residual tumor (Net Reclassification Index [NRI] for ypT1-4 group =0.339, 95%CI: 0.204-0.482, p<0.001). Multivariate logistic regression analysis demonstrated that the yT stage based on CE-3 MRI was the sole independent predictor of pCR after NCRT (P < 0.001).
Conclusion:
CE MRI can identify residual tumor more precisely. In particular, CE-3 MRI series demonstrated superior diagnostic efficacy and good inter-observer agreement, which helps prevent missed diagnoses and provides clinicians with a more stable and reliable imaging assessment protocol.
