Evaluation Of MRI On SIB-IMRT In Neoadjuiant Chemoradiotherapy For Rectal Cancer And Its Value In Predicting Curative Effect

Objective: To compare the effect of simultaneous integrated boost intensity-modulated radiation therapy(SIB-IMRT)and regular intensity-modulated radiotherapy(R-IMRT)technique in preoperative concurrent chemoradiotherapy treatment of locally advanced rectal cancer,to evaluate the feasibility of SIB-IMRT use in chemoradiotherapy for locally advanced rectal cancer,as well as to predict the value of complete response through volume of MR,magnetic resonance diffusion-weighted imaging(DWI)and dynamic contrast-enhanced magnetic resonance imaging(DCE-MRI).Materials and Methods: Sixty-seven patients were included in this study,and they were randomly divided into SIB-IMRT group(n=39)and R-IMRT group(n=28).All patients underwent MR examination before neoadjuvant chemoradiotherapy and neoadjuvant therapy,and all were treated with TME surgery.Post-processing obtains the parameters of volume,ADC value,Ktransvalue,and the rate of change ?Volume%,?ADC%,?Ktrans% were calculated before and after treatment.The postoperative pathological tumor regression scores were based on the Mandard criteria.The experimental group and the control group were the pCR group and the non-pCR group,respectively.The ROC analysis was used to compare the predictive efficacy value,sensitivity and specificity.Results: 1.After the neoadjuvant treatment,the volume of the experimental group was reduced and the Ktrans value was significantly lower than that of the control group,the difference was statistically significant(P = 0.007,0.020,respectively,<0.05),and the ?Volume% in the experimental group and the control group also have statistical significance(P value = 0.002,<0.05).2.In pCR group,the increase of ADC value of the tumor in SIB-IMRT group and the tumor volume reduction rate(?Volume%)was better than that of the R-IMRT group(P value 0.043,0.015,both <0.05);In non-pCR group,the tumor volume reduction and Ktrans value reduction were better in the SIB-IMRT group than in the R-IMRT group(P value = 0.021,0.032,<0.05).3.The ROC diagnostic test evaluates the diagnostic efficacy of the change ratios of ?Volume%,?ADC%,and ?Ktrans% with respect to the volume,ADC,and Ktrans values,before and after the neoadjuvant in the experimental group and the control group.In these cases,the experimental group volume change rate(?Volume%)has higher diagnostic efficiency,the AUC is 0.734,and the critical value is more than46.5%,the sensitivity is 81.3%,the specificity is 65.2%,and the ADC changerate AUC is 0.698,the P values were 0.014 and 0.037,respectively,and were both <0.05.Conclusion: 1.The SIB-IMRT technique is a better treatment compare to R-IMRT in the application of preoperative concurrent chemoradiotherapy for locally advanced rectal cancer in terms of tumor volume reduction,volume reduction rate,ADC value increase and Ktrans value decrease.2.The tumor volume reduction rate(?Volume%)and ADC increase rate(?ADC%)are helpful to predict the pathological complete remission after neoadjuvant chemoradiotherapy for locally advanced rectal cancer.