Abstract:

Objective To explore the predictive value of a nomogram model based on multimodal MRI quantitative parameters for the efficacy of neoadjuvant chemotherapy in rectal cancer. Methods The case data of 106 patients with advanced rectal cancer who received neoadjuvant chemotherapy with the XELOX regimen （oxaliplatin+capecitabine） at the Department of Gastrointestinal Surgery， Nanping First Hospital Affiliated to Fujian Medical University from May 2022 to March 2025 were retrospectively collected. The tumor regression grade （TRG） was evaluated according to the Modified Ryan grading system. The general clinical data and multimodal MRI quantitative indicators T1 value， T2 value， apparent diffusion coefficient （ADC）， volume transport constant （K^trans）， flux rate constant （K_ep）， volume fraction of extravascular extra vascular space （V_e） of patients with different chemotherapy efficacy were compared. A multivariate logistic regression was used to screen the independent influencing factors of the efficacy of neoadjuvant chemotherapy in patients with rectal cancer. A nomogram model was constructed based on the results of multivariate analysis. The predictive efficacy of the model was evaluated using the receiver operator characteristic （ROC） curve， the consistency between the predicted values and the actual values was verified using the calibration curve， and the net benefit and practicability of the model in clinical practice were evaluated through the decision curve. Results Among 106 rectal cancer patients， there were 3 cases of TRG grade 0， 10 cases of grade 1， 32 cases of grade 2， and 61 cases of grade 3. The treatment inefficiency rate was 57.55% （61/106）. There were statistically significant differences in age, TNM stage and degree of differentiation between the ineffective and effective patients （t=3.14， P=0.002； χ²=4.62， P=0.032； χ²=5.17， P=0.023）. The ADC values of patients with ineffective and effective treatment were （1.06±0.14）×10^-3 and （1.18±0.14）×10^-3 mm²/s， respectively， while the K^trans values were （0.24±0.08） and （0.18±0.06） /min， the K_ep values were （1.12±0.34）， （0.88±0.12） /min， and the V_e values were 0.29±0.11 and 0.21±0.06， respectively， with statistically significant differences （t=4.32， P<0.001； t=4.18， P<0.001； t=5.05， P<0.001； t=4.58， P<0.001）. Multivariate analysis showed that， ADC （OR=0.01， 95%CI： 0.01-0.08， P=0.001）， K^trans （OR=1.12， 95%CI： 1.03-1.22， P=0.008）， K_ep （OR=9.09， 95%CI： 5.08-7.12， P<0.001）， V_e （OR=1.11， 95%CI： 1.04-1.19， P=0.003） were independent factors affecting the efficacy of neoadjuvant chemotherapy in patients with rectal cancer. Based on this， a nomogram model was constructed， and the ROC curve analysis showed that the areas under the curve （AUCs） for predicting the efficacy of neoadjuvant chemotherapy in rectal cancer patients by ADC， K^trans， K_ep， V_e， and the nomogram model were 0.73， 0.70， 0.76， 0.71， 0.88， respectively. The predictive value of the nomogram model was higher than that of ADC， K^trans， K_ep， and V_e alone （Z=2.24， P=0.025； Z=2.51， P=0.012； Z=3.49， P<0.001； Z=2.07， P=0.039）. The internal validation of the Bootstrap method showed that the consistency index of the nomogram model for predicting the efficacy of neoadjuvant chemotherapy for rectal cancer was 0.875， and the calibration curve showed that the predictive probability of the model was close to the actual probability. The decision curve showed that the nomogram model could provide a higher clinical net rate of return and had certain clinical practicability. Conclusions The ADC， K^trans， K_ep， and V_e parameters of multimodal MRI are independent influencing factors of the efficacy of neoadjuvant chemotherapy in rectal cancer patients. A nomogram model based on these four parameters has a certain predictive power for the efficacy of neoadjuvant chemotherapy in patients， and shows good predictive performance within this study.

Key words: Rectal neoplasms, Magnetic resonance imaging, Neoadjuvant chemotherapy, Prediction model