Application Research Of Magnetic Resonance Imaging In And Preoperative Staging Of Rectal Cancer And The Assessment Of CRM

BackgroundColorectal cancer is a common disease threat to people’s health in China and is aserious threat to human health. In recent years, the morbidity of this disease has increasedalong with the improvement of national living standards. It is reported that the morbidity ofrectal cancer is the third highest, just lower than that of lung cancer and gastric cancer. Theprimary treatment approach for rectal cancer is surgery. Accurate staging and locating oftumors as well as appropriate surgical technique are essentially necessary for successfulsurgery. Preoperative staging plays a pivotal role in clinical decision-making preoperativeneoadjuvant therapy、operation method、surgical outcomes and postoperative treatment ofrectal cancer. In the normalization of treatment, quality control of surgery as well aspostoperative pathological evaluation, more and more emphasis on CRM is mentioned. Ifthe result is CRM+, patients should be treated with preoperative Chemotherapy andRadiation. The patients shouldn’t accept the surgery until it turns to CRM-. CRM+oftenleads to bad postoperative restore of patients. The imaging examination is essentiallyimportant for the preoperative staging and CRM evaluation of rectal cancer. MRI has highsoft tissue resolution, which is important for the preoperative staging as well as CRMevaluation.ObjectiveWe compare the results of3.0T magnetic resonance imaging for having colonoscopyconfirmed，there is a clear pathological diagnosis of colorectal cancer patients and thepostoperative final diagnosis, which is used as golden standard to discuss the accuracy ofMRI for preoperative TN staging of rectal cancer and the status of CRM.MethodsWe collected90patients with rectal cancer which had been proven by the pathologicalexamination between2010.1and2012.4in our hospital. Normal MRI scan of rectal (including T1WI T2WI T2-SPAIR and DWI) had been conducted for all patients. Ifpossible, enhancing scan was also performed. The scope of scan spanned from the terminalof rectal to anus. We used Multi-dimensional imaging to observe the form, site and signalintensity of tumors, the depth of transmural invasion, the density and size of lymph nodesas well as the status of CRM. We also analyzed the curve distance from the anal verge totumors. Using pathological examination as golden standard, we utilized SPSS13.0toperform the data analysis, to evaluate the accuracy, sensitivity, positive predictive valueand negative specificity value of MRI3.0T for the determination of TN staging of rectalcancer as well as the status of CRM.ResultThe pathological staging results showed that all90patients included4T1-staging,33T2-staging,43T3staging and10T4-staging ones. The MRI results of80patients werecorrect, with4higher and6lower staging ones. One T1-staging patient was reportedincorrectly as T2-staging, two T2-staging ones as T3-staging, one T2-staging one asT1-staging, four T3-staging ones as T2-staging, one T3-staging one as T4-staging and oneT4-staging one as T3-staging. The MRI T-staging results were highly consistent withpathological ones (Kappa=0.771, P=0.000) and the accuracy rate was88.9%(80/90).The pathological evaluation of lymph nodes manifested65of these patients were lymphnode metastasis，with25were without lymph node metastasis.The MRI showed53ofthese patients were lymph node metastasis，with37were without lymph node metastasis。The MRI N-staging results had moderate consistency with that of pathological examination(Kappa=0.540, P=0.009). The accuracy of lymph nodes staging of MRI was77.8%(70/90), with the sensitivity of70.8%(46/65) and specificity of96.0%(24/25). Thepathological results showed that12of them were CRM+and78of them were CRM-.82ofthem were correctly diagnosed by MRI. Two of the12CRM+patients were incorrectlydiagnosed as CRM-, and six of the78CRM-patients were incorrectly diagnosed as CRM+.The results of MRI and pathological analysis for CRM were highly consistent. Thesensitivity of MRI for CRM evaluation was83.3%(10/12), the specificity was92.3%(72/78) and the accuracy was91.1%(82/90). There is no significant statistical differencebetween MRI and resected specimens when we measured the distance from the anal vergeto tumor (t=1.844，P=0.077).ConclusionMRI is highly accurate for the TN-staging and CRM evaluation. MRI can be used toshow the local lesion and adjacent organs clearly as well as precisely measure the distance between tumors and anal verge. MRI plays an important role in the decision of individualtreatment program and the choice of optimum surgical modality.