Application Of MRI In Accurate Staging And Precise Localization Of Rectal Cancer Before Operation

Objective:To evaluate the value of rectal MRI in preoperative staging of rectal cancer,mesorectal fascial infiltration and measurement of distance.Clinical data and methods:From October 2016 to June 2018,62 patients with rectal cancer confirmed by pathology were selected.There were 40 males and 22 females,from 34 to 81 years old.The mean age was(60.68 ±12.70)years.All patients were examined by Magnetic resonance imaging(MRI)before operation.The preoperative MRI staging of rectum was compared with the postoperative pathological staging of rectal cancer;the consistency of preoperative rectal MRI and postoperative pathology in the diagnosis of mesorectal fascial infiltration was analyzed.The consistency analysis of the nature of cumferential resection margin,CRM was carried out,and the distance from the lower margin of the tumor to the anal margin displayed by the rectal MRI was compared with the data of the same site measured immediately at the time of resection of the specimen.The apparent diffusion coefficient(ADC)of rectal cancer with different degrees of differentiation was statistically analyzed.Results:Between 62 patients,the overall accuracy rate of T staging with rectal MRI was 88.7%(55 / 62),including 80%(4 / 5)for T1 staging and84.6%(11 / 13)for T2 staging,respectively.The correct rate of T 3 and T4 staging were 91.7%(33 / 36)and 87.5%(7 / 8),respectively.The accuracy,sensitivity,specificity,positive predictive value and negative predictive value of high resolution MRI for preoperative T1~T4 staging of rectal cancer are followed bellow: T1 were 98.4%,80.0%,100%,100%,98.3%,respectively;T2: 93.5%,84.6%,95.9%,84.6%,95.9%;T3:90.3%,91.7%,88.5%,91.7%,88.5%;T4 stage: 95.2%,87.5%,96.3%,77.8%,98.1%.The MRI staging of rectal cancer was consistent with pathological T staging(Kappa=0.837,p < 0.001),and the overall accuracy of N staging was 77.4%(48 / 62).The correct rate of N0,N1 and N2 staging were 78.1%(25/32),77.8%(14/18),75%(9/12)respectively.The accuracy,sensitivity,specificity,positive predictive value and negative predictive value of high resolution MRI in preoperative N0~N2 staging of rectal cancer were followed bellow: N0,83.9%,78.1%,90.0%,89.3%,79.4%;N1,82.3%,77.8%,84.1%,66.7%,90.2%;N2,88.7%,75.0%,92.0%,69.2%,93.9%.The N staging of MRI and pathological N staging of rectal cancer were moderate(Kappa=0.64,p < 0.001).Rectal MRI and pathology are in good agreement in the diagnosis of mesorectal fascial infiltration(Kappa=0.794,p < 0.001).The distance from the lower margin of the tumor measured by rectal MRI to the anal margin was small to that measured at the same site when the specimen was cut off,and the difference was not statistically significant.The ADC value increased with the degree of differentiation of rectal cancer,and the difference was statistically significant(P < 0.001).Conclusion:MRI has high accuracy in the diagnosis of pre-operative T stages of rectal cancer and moderate accuracy in N stages.It can accurately judge the nature of mesorectal fascia in rectal cancer and can accurately measure the distance from the lower margin of rectal tumor to the anal margin.MRI can accurately reflect the differentiation degree of rectal cancer at the same time.The advantages of rectal MRI are helpful to guide rectal cancer patients to make a reasonable diagnosis,treatment plan and evaluate prognosis.It has high clinical application value,and is worth popularizing in clinical work.