Based On The Application Of MRI For Rectal Tumor Staging And Measurement In The Assessment Of Anal Preservation

Background and aims:Rectal cancer is a common gastrointestinal malignancy.With the changes of people’s living environment and habits,the incidence of rectal cancer has a clear upward trend,as well as has become more rejuvenated in China.Early diagnosis and selection of the appropriate therapeutic methods are of great significance for prolonging the life of patients and improving their quality of life.As for patients with rectal cancer,surgical resection is still the major strategy for treatment.What’s more,the stage and height of the tumor is crucial to the election of surgical timing and method.With the development of imaging techniques and the clinical application of magnetic resonance imaging(MRI),the preoperative staging and height measurements of rectal cancer have become more diverse.How to accurately determine the staging and height of tumor is an important link between the diagnosis and treatment of rectal cancer.The purpose of this study was to determine the rectal tumor stage and measure the height of rectal tumor based on the MRI image characteristics,and to evaluate the application value of MRI in predicting of anal sphincter preservation and estimate whether the anus-saving distance is different between males and females.Methods:This study is a retrospective study.Patients diagnosed as rectal cancer in the Department of Anorectal and General Surgery of the Affiliated Hospital of Nanjing University of Traditional Chinese Medicine,during January 2010 to July 2018,as well as,accepting preoperative MRI of rectum and radical operation,were recruited in this study.Radiologists performed preoperative evaluation according to the imaging features of rectal cancer.Pathological staging was referred to the seventh edition of the AJCC Cancer Staging Manual.The distance from the distal end of the rectal tumor to the anorectal ring(ARR)and the anal verge(AV)was measured by MRI.The height of the tumor measured by fiber colonoscopy and digital rectal examination was recorded in the patient’s medical records.The ROC(receiver operator characteristic)curve was used to analyze the accuracy of MRI,fiber colonoscopy and digital rectal examination measurements.The distance difference of anal sphincter preservation was evaluated according to Yoden index.Result:152 patients with rectal cancer were included in this study.The preoperative stage of MRI was 0/8(0.0%)in T1,2/39(5.1%)in T2,82/102(80.4%)in T3,2/3(66.7%)in T4,24/92(26.1%)in N0,14/33(42.4%)in N1,16/27(59.3%)in N2.There were no correlations between preoperative staging and anal sphincter preservation(P>0.05).Anal sphincter preservation was performed in 111 patients(73.0%).In the assessment of anal sphincter preservation,the cut-off values of the distance from the tumor distal end to ARR and AV were 3.7cm and 6.7cm,respectively.Both ARR and AV can be used as distal reference markers for MRI measurement of rectal tumor height,AUC(area under ROC)values were 0.882(95%CI,0.820-0.929)and 0.862(95%CI,0.797-0.913),respectively,P=0.19.The cut-off values of male and female in anal sphincter preservation were 3.7cm(ARR),6.7cm(A/V)and 2.5cm(ARR),5.9cm(AV),respectively.63 patients had tumor height measured by MRI,fiber colonoscopy and digital rectal examination,of which 48 cases(76.2%)had anal sphincter preservation.The cut-off values of the distance from tumor distal end to ARR and AV were 3.7cm and 6.7cm,respectively.The fiber colonoscopy and digital rectal examination were 4.0cm and 4.0cm,respectively.Compared with fiber colonoscopy and digital rectal examination,the rectal tumor height measured by MRI is better than fiber colonoscopy and digital rectal examination where AV was considered as the reference marker,AUC values are 0.800(95%CI,0.680-0.890),0.698(95%CI,0.569-0.807)and 0.715(95%CI,0.587-0.821),respectively.Conclusion:MRI has higher accuracy in preoperative T3 and T4 staging of rectal cancer,but N staging is not good.MRI is more accurate in measuring the height of rectal cancer than fiber colonoscopy and digital rectal examination,which can be used as an effective supplement for fiber colonoscopy and digital rectal examination.Both ARR and AV can be used as reference markers for measurement when performing MRI measurements before surgery.Preliminary results of the study show that the distance of the anal sphincter preservation in male is about 1cm higher than that in female.