Radiologic And Pathological Comparison Of T-Staging Of Rectal Cancer With 3.0 Tesla High-resolution Magnetic Resonance Imaging

[Background and Objective]Rectal cancer is the most common malignant tumors, the incidence rate in the world ranking the forefront of the incidence of cancer, and with the improvement of people’s living standards, and meat protein in the diet increased the proportion of the structure, the incidence is rising. Rectal cancer has become a major public health problem in the community, the key is early diagnosis and treatment of discovery, the prognosis depends largely on the time of clinical tumor stage performance. This information helps select patients who need to receive neoadjuvant therapy. Therefore, an accurate preoperative diagnosis and staging of colorectal cancer is becoming increasingly important. This applies especially to cases with locally advanced rectal cancer, in order to maximize the chances of a complete resection and survival, and at the same time, to minimize morbidity and loss of quality of life. Besides, accurate preoperative staging can assist in pre-surgical planning and can help evaluate prognosis and reduce the rate of local recurrence.In the diagnosis of rectal cancer, including rectal wall invasion, mesangial infiltration, circumferential resection margin (CRM), and the existence of distant metastasis violations must accurately determine the structure of the surrounding tissue, which is essential for planning treatment. If the tumor is confined to the rectal wall, it can fundamentally treated by local excision alone; and tumors that penetrate mesorectal require neoadjuvant chemotherapy to make them fall on or complete remission before surgical treatment, which can effectively improve the prognosis. Total mesorectal excision (TME) is the surgical gold standard for surgical treatment of rectal cancer, the surgical approach is based on the anatomy of the pelvic foundation. TME is the complete excision of the mesorectal fascia that wraps fat, lymph nodes, blood vessels, nerves and other loose connective tissue. In the past few decades, more and more widely used TME surgery makes the local recurrence rate of rectal cancer had a significant decline. When performing TME, we have to know about the relationship between the tumor and the circumferential resection margin, that is very important. If CRM is positive, a high risk of local recurrence happened. Because the rectum and mesorectum will be excised totally at the mesorectal fascia plane, we use mesorectal fascia on behalf of potential CRM of patients undergoing surgery TME. Therefore, a good imaging can show the precise anatomical detail, in order to accurately preoperative staging, which is critical for rectal cancer patients.In the conventional, in the imaging for rectal cancer staging, Barium enema can show intestinal lesion morphology and dynamics, the presence or absence of mucosal folds damage, and the lesion location and vertical scope of involvement. However, the tissues around the rectum and surrounding organs with or without violations can not be displayed. The endorectal ultrasound(EUS) is considered the reference standard to assess the depth of rectal wall invasion. EUS can accurately superficial staging rectal cancer, but it is limited in advanced tumor staging, because the sonar is usually unable to assess the depth of penetration of advanced disease. EUS in assessing the mesorectal and adjacent organ invasion, regional lymph node is ineffective. Additionally, there are other restrictions including the dependence of the proficiency and the diagnostic level of the operator, patient tolerance, and the proximal tumors can not be checked because of severe stenosis of some rectal lumen. Thus, EUS has a high degree of accuracy in the evaluation of early-stage tumors, but not suitable for the evaluation of advanced rectal cancer. Multi-slice spiral computed tomography(MSCT), although the effectiveness of the staging of rectal cancer has a significant improvement recently, but not reliably distinguish between the rectal wall layers and effective display mesorectal fascia, adequate local tumor staging for rectal wall layer and perirectal infiltration correct assessment is still insufficient. Magnetic resonance imaging (MRI) is one of the most effective means of early detection of colorectal cancer with its excellent soft tissue resolution, multi-parameter, multi-directional characteristics, and it can accurately show mesorectal fascia and the anatomy of the rectal cancer and plays a unique advantage in early diagnosis and staging.High-resolution magnetic resonance imaging (HR-MRI) is a T2WI imaging with a small field of view, thin section and perpendicular or parallel to the traveling direction of the bowel and with higher spatial resolution. HR-MRI has a high soft tissue resolution, multi-dimensional imaging and has a higher spatial resolution compared with conventional MRI sequences. In recent years, HR-MRI study of rectal cancer staging gradually becomes a hot topic in western developed countries. Some domestic 1.5T HR-MRI staging of rectal cancer reported but 3.0T HR-MRI staging of rectal cancer are few reports.In this study, a group of patients with primary rectal cancer as research subjects underwent preoperative 3.0T HR-MRI examination, all patients underwent surgery and pathology results obtained. Two experienced doctors take a double-blind evaluation of the images, according to the MRI features and the extent of the bowel infringement of the tumors to determine T staging, assess the degree of accuracy of local tumor invasion, and compare with pathological T stage, assess the accuracy of prognosis of HR-MRI of tumor extent of local invasion, and evaluate the clinical value of HR-MRI sequences.[Materials and Methods]1.Clinical informationWe collected 51 patients with primary rectal cancer confirmed by pathology during October 2014 to March 2015 in General Surgery, Nanfang Hospital, took MRI exam before surgery, in all cases within seven days of surgery and pathology results obtained. There are 37 males and 14 females, aged 34 to 79 years, with an average age of 56.9±7.9 years.1.1 Inclusion criteria:(1) Patients with histologically proven rectal cancer;(2) Did not undergo radiotherapy and chemotherapy before surgery.1.2 Exclusion criteria:(1) Patients without surgery and histologically proven rectal cancer;(2) Surgical specimens of patients did not complete pathological data;(3) Patients underwent radiotherapy and chemotherapy before surgery;(4) Image quality is poor, making it impossible to diagnose or is likely to affect the diagnosis.2. Methods2.1 EquipmentPhilips Achieva 3.0 Tesla magnetic resonance, abdominal 16-channel phased-array surface coil. Observing and evaluation of image were on Philips diagnostic workstation.2.2 Method of operationPatients were given water enema to clean the rectum and giving intestinal antispasmodic agent Anisodamine injection (10mg) intramuscularly in about two hours before the MR examination. Patient are at supine scanning position.2.3 Sequence protocolsthe sequences are in the following order:Axial T2-weighted SPAIR(spectral adiabatic inversion recovery) fat-suppressed sequence:Slice thickness was 6 mm with gap 0.6 mm, field of view was 30 cm,matrix was 400×312. Repetition time (TR) was 4000ms, Echo time(TE) was 100ms. The entire pelvic was covered;Sagittal high-resolution T2-weighted turbo(TSE) sequence:Slice thickness was 3 mm without gap, field of view was 24 cm,matrix was 400×400. TR was 5000ms, TE was 100ms;Oblique axis perpendicular to the rectal length high-resolution T2-weighted turbo(TSE) sequence:Slice thickness was 3 mm without gap, field of view was 16 cm, matrix was 256 x256. TR was 5000ms, TE was 100ms;For low rectal tumors, oblique coronal parallel to the rectal length high-resolution T2-weighted turbo(TSE) sequence obtained:Slice thickness was 3 mm without gap, field of view was 16 cm,matrix was 256 x256. TR was 5000 ms, TE was 100 ms;Axial T1-weighted turbo spin-echo (TSE) sequence:Slice thickness was 5 mm with gap 0.5 mm, field of view was 30 cm,matrix was 300 x234. Repetition time (TR) was 430 ms, Echo time (TE) was 10 ms. The entire pelvic was covered.The overall examination time taked about 45 minutes.2.4 Image evaluationTwo experienced doctors take a double-blind evaluation of the images, according to the MRI features and the extent of the bowel infringement of the tumors to determine T staging. If the evaluation results are inconsistent, consensus through discussion. MRI staging referring to 2010 American Joint Committee on Cancer (AJCC)/Union for International Cancer Control(UICC) 7th edition TNM staging system developed, such as the evaluation criteria given below:Stage T1:Tumor confined to the submucosa, but that does not infringe the muscularis propria.Stage T2:tumor invades the muscularis propria, but does not penetrate the muscularis propria; no tumor seen within the perirectal fat.Stage T3:tumor penetrates muscularis propria into the subserosa, or into non-peritonealized pericolic or perirectal tissue.Stage T4:tumor invades adjacent pelvic organs. Among them, the invasion of the peritoneal reflection as T4a, invasion of other adjacent organs as T4b.2.5 Statistics analysisClassified the MRI T-staging data and each postoperative pathological T-staging data of rectal cancer, applied SPSS 19.0 software for analysis and calculated the accuracy, sensitivity, specificity, positive predictive value(PPV), negative predictive value(NPV) of HR-MRI for preoperative T staging of rectal cancer. Applied Kappa test and Spearman rank correlation and compared the consistency and relevance of HR-MRI T staging with pathologic T staging of rectal cancer[Results]In our study, HR-MRI T-staging accuracy was 84.3%(43/51). The accuracy rate of T1 stage was 66.7%(2/3), one case of Tl patients over stage T2; the accuracy rate of T2 stage was 75.0%(9/12), including three cases of T2 patients being overstaging T3; the accuracy rate of T3 stage was 86.2%(25/29), including three cases of T3 patients being understaging T2,one case of T3 patients being overstaging T4; the accuracy rate of T4 stage was 100%(7/7). The accuracy, sensitivity, specificity, positive predictive value, negative predictive value of HR-MRI for prediction of T1-T4 stage were 98.04%,66.67,l00.00%,100.00%,97.96% and 90.20%,75.00%, 94.87%,81.82%,92.50% and 86.27%,86.21%,86.36%,89.29%,82.61% and 94.12%,100.00%,93.18%,70.00%,100.00%, respectively.The results of HR-MRI and pathologic T-staging for rectal cancer consistency check were Kappa= 0.740, P <0.01, Kappa 95% confidence interval 0.573-0.907. The results of HR-MRI and pathologic T-staging for rectal cancer Spearman rank correlation were r=0.838, P< 0.01.[Conclusions]1.High-resolution MRI can clearly display rectal cancer lesions and rectum, mesorectal, mesorectal fascia and adjacent tissues, and the operation is relatively simple. It can be a good assessment of the extent of rectal cancer extramural invasion, circumferential resection margin involvement, peritoneal involvement and adjacent organs violated on HR-MRI.2. HR-MRI T-staging for rectal cancer are highly consistent and correlated with pathological examination.3.HR-MRI T-staging for rectal cancer is with high accuracy and help guide the development of treatment programs and assess prognosis. HR-MRI has a high clinical significance, worthy of promotion in clinical work.