核磁影像在直肠癌诊疗中的应用现状

直肠癌是我国最常见的恶性肿瘤之一,新辅助放化疗配合TME手术是局部晚期直肠癌的标准治疗模式。核磁影像可以为直肠癌的诊疗提供解剖定位、临床分期与新辅助放化疗后的疗效评价等多方面信息,从而为综合治疗方案的精准制订提供支持帮助。文章旨在对核磁影像对直肠癌分期、疗效评价及预测的应用现状及发展趋势进行综述。     

Rectal cancer staging

Endorectal-US is the most suitable imaging technique in the initial staging of rectal cancer and it is mostly accurate in evaluating early stages and in demonstrating the perirectal spread of cancer tissue. CT is not able to demonstrate the layers of the rectal wall and its accuracy in demonstrating the invasion of muscolaris propria and perirectal fat is lower than other techniques, so its use in local staging is not recommended. MRI is mostly accurate in evaluating the mesorectum and the mesorectal fascia which are considered the most relevant prognostic factors for local recurrence. Lymph node evaluation is a challenge for every imaging techniques since lymph node size is not a reliable criterion for diagnosing metastatic involvement. Nuclear medicine has a remarkable role in the work-up of rectal cancer and in the next future the combination of FDG PET in conjunction with a dedicated contrast enhanced CT protocols could become a single-step staging procedure.     

高分辨3.0T磁共振评估直肠癌术前环周切缘有无累及的前瞻性研究

目的:探讨高分辨3.0T磁共振(magnetic resonance imaging,MRI)对直肠癌术前环周切缘(circumferential resection margin,CRM)有无累及的前瞻性评估,以指导直肠癌的多学科诊断和个体化治疗方式。方法:2012年2月至2017年7月利用GE 3.0T磁共振对46例经结肠镜证实的直肠癌患者进行盆腔磁共振平扫、DWI检查,常规序列包括失状位FRFSE T2WI、冠位FRFSE T2WI、轴位FRFSE T2WI和DWI,并且所有T2WI序列都采用小视野、薄层扫描,DWI的b值取1 000 s/mm2。然后综合所有序列对直肠癌病灶进行术前MRI-T、N分期判定,评估直肠系膜筋膜、环周切缘有无累及,然后与手术病理结果进行对照分析。结果:在46例直肠癌中,MRI-T分期中正确诊断40例,错误诊断6例,正确率为87.0%。N分期中正确诊断34例,错误诊断12例,正确率为73.9%。MRI判断直肠系膜环周切缘有无累及的准确率、敏感性、特异性、阳性预测值及阴性预测值分别为93.5%、100.0%、91.2%、80.0%及100.0%。结论:高分辨率3.0T磁共振成像可以对直肠癌手术环周切缘有无累及进行准确的预测,还可以清楚的显示病灶及邻近组织侵犯情况,指导直肠癌的个体化治疗。     

Role of Combined-Modality Therapy in the Management of Locally Advanced Rectal Cancer

The majority of patients with nonmetastatic rectal cancer are candidates for an aggressive multimodality approach with curative intent. Preoperative staging is critical in determining which patients should be offered neoadjuvant therapy. Available staging tools include digital rectal examination, transrectal ultrasound, computed tomography, positron-emission tomography, and magnetic resonance imaging scans. Magnetic resonance imaging has emerged as the most accurate staging modality in experienced centers. Multidisciplinary preoperative patient evaluation, better staging techniques, neoadjuvant chemoradiation, acceptance of shorter distal rectal margins, and transanal excision of T1 N0 rectal tumors in close proximity to the anal sphincter have resulted in decreased rates of abdominoperineal resections. Total mesorectal excision has been adopted as the standard surgical approach because of a reduction in rates of pelvic relapse. Preoperative and postoperative radiation therapy was shown to decrease the local recurrence rate, but not overall survival, in patients with resectable rectal cancer. The addition of chemotherapy to radiation was consistently shown to improve local control, and in some trials, improved overall survival. Neoadjuvant combined chemotherapy and radiation therapy are superior to adjuvant combined-modality therapy because of higher rates of sphincter preservation, less toxicity, and lower local recurrence rates. For patients with stage II or III disease, neoadjuvant continuous-infusion 5-fluorouracil (5-FU), concurrently with pelvic radiation, followed by postoperative 5-FU–based chemotherapy, remains the standard multimodality approach. Ongoing trials are testing the integration of newer cytotoxic agents such as capecitabine, oxaliplatin, irinotecan, and biologic agents such as cetuximab and bevacizumab to chemoradiation.     

MRI assessment and outcomes in patients receiving neoadjuvant chemotherapy only for primary rectal cancer: long-term results from the GEMCAD 0801 trial

BackgroundPrimary chemotherapy has been tested as a possible approach for patients with high risk features but predicted clear mesorectal margins on preoperative MRI assessment. This study investigates the prognostic relevance of baseline and post-treatment MRI and pathology staging in rectal cancer patients undergoing primary chemotherapy.Patients and methodsForty-six patients with T3 tumour > =2 mm from the mesorectal fascia were prospectively treated with Neoadjuvant Capecitabine, Oxaliplatin and Bevacizumab prior to surgery between 2009 and 2011. The baseline and post-treatment MRI: T, Nodal and Extra-mural venous invasion (EMVI) status were recorded as well as post-treatment MRI Tumour regression grade (TRG) and modified-RECIST assessment of tumour length. The post-treatment pathology (yp) assessments of T3 substage, N, EMVI and TRG status were also recorded. Three-year disease-free survival (DFS) and cumulative incidence of recurrence were estimated by using the Kaplan–Meier product-limit method, and Cox proportional hazards models were used to determine associations between staging and response on MRI and pathology with survival outcomes.ResultsAbout 46 patients underwent neoadjuvant chemotherapy alone for high risk margin safe primary rectal cancer. The median follow-up was 41 months, 5 patients died and 11 patients experienced relapse (2 local, 8 distant and 1 both). In total 23/46 patients were identified with MRI features of EMVI at baseline. mrEMVI positive status carried independent prognostic significance for DFS (P = 0.0097) with a hazard ratio of 31.33 (95% CI: 2.3–425.4). The histopathologic factor that was of independent prognostic importance was a final ypT downstage of ypT3a or less, hazard ratio: 14.0 (95% CI: 1.5–132.5).ConclusionsmrEMVI is an independent prognostic factor at baseline for poor outcomes in rectal cancer treated with neoadjuvant chemotherapy while ≤ypT3a is associated with an improvement in DFS. Future preoperative therapy evaluation in rectal cancer patients will need to stratify treatment according to baseline EMVI status as a crucial risk factor for recurrence in patients with predicted CRM clear rectal cancer.     

中低位进展期直肠癌患者全直肠系膜切除术前应用同步新辅助放化疗效果分析

目的：分析中低位进展期直肠癌患者全直肠系膜切除术前同步新辅助放化疗应用疗效。方法选取45例中低位进展期直肠癌患者为研究对象,将其随机分为联合组（23例）与对照组（22例）,对照组患者行单纯全直肠系膜切除术,联合组患者在行全直肠系膜切除术前同步新辅助放化疗,比较联合组新辅助放化疗前后肿瘤分期（TNM）情况,两组患者治疗前后肿瘤标志物水平变化情况及术后3个月保肛率、复发率、转移率、术后并发症发生情况。结果新辅助治疗后联合组TNM分期较治疗前降低,差异具有统计学意义（P﹤0.05）;治疗前两组患者癌胚抗原（CEA）、糖链抗原19-9（CA19-9）、糖链抗原242（CA242）水平差异无统计学意义（P﹥0.05）,治疗后均降低（P﹤0.05）,且联合组低于对照组（P﹤0.05）;两组患者术后3个月转移率及并发症发生率差异无统计学意义（P﹥0.05）,联合组保肛率高于对照组,复发率低于对照组（P﹤0.05）。结论采用全直肠系膜切除术前同步新辅助放化疗,可以有效提高中低位进展期直肠癌患者保肛率,降低复发率,改善肿瘤TNM分期,降低CEA、CA19-9、CA242水平,具有良好的应用前景。     

Moderne Bildgebung beim Rektumkarzinom

Colorectal cancer is one of the most common malignant diseases. Accurate preoperative staging is of great importance in order to provide patients with optimal treatment. There are various imaging modalities for staging rectal cancer according to the TNM system. For local staging, endorectal ultrasound (EUS) and magnetic resonance imaging (MRI) are the most suitable imaging tools. With modern high resolution MRI scans infiltration of the mesorectal fascia can be assessed with a high degree of accuracy, an important aid for decision-making with respect to respectability and prognosis of rectal cancer. On the other hand, due to technical limitations it is not possible to perform staging of distant metastases with MRI in the same examination. For this purpose computed tomography (CT) remains the optimal method. Further research is required to define the role of PET and PET/CT in the staging of rectal cancer.     

Effectiveness of preoperative staging in rectal cancer: digital rectal examination,endoluminal ultrasound or magnetic resonance imaging?

In rectal cancer, preoperative staging should identify early tumours suitable for treatment by surgery alone and locally advanced tumours that require therapy to induce tumour regression from the potential resection margin. Currently, local staging can be performed by digital rectal examination (DRE), endoluminal ultrasound (EUS) or magnetic resonance imaging (MRI). Each staging method was compared for clinical benefit and cost-effectiveness. The accuracy of high-resolution MRI, DRE and EUS in identifying favourable, unfavourable and locally advanced rectal carcinomas in 98 patients undergoing total mesorectal excision was compared prospectively against the resection specimen pathological as the gold standard. Agreement between each staging modality with pathology assessment of tumour favourability was calculated with the chance-corrected agreement given as the kappa statistic, based on marginal homogenised data. Differences in effectiveness of the staging modalities were compared with differences in costs of the staging modalities to generate cost effectiveness ratios. Agreement between staging and histologic assessment of tumour favourability was 94% for MRI (kappa=0.81, s.e.=0.05; kappa(W)=0.83), compared with very poor agreements of 65% for DRE (kappa=0.08, s.e.=0.068, kappa(W)=0.16) and 69% for EUS (kappa=0.17, s.e.=0.065, kappa(W)=0.17). The resource benefits resulting from the use of MRI rather than DRE was 67164 UK pounds and 92244 UK pounds when MRI was used rather than EUS. Magnetic resonance imaging dominated both DRE and EUS on cost and clinical effectiveness by selecting appropriate patients for neoadjuvant therapy and justifies its use for local staging of rectal cancer patients.     

Optimizing rectal cancer surgery by total mesorectal excision and “cylindrical” extralevator techniques for abdominoperineal excision

Since total mesorectal excision for rectal cancer was first described in 1988, widespread adoption of this technique has improved oncologic outcomes significantly. However, improved survival and decreased local recurrence rates in patients having anterior resection have not translated into equivalent improvements in those having abdominoperineal excision and permanent stoma. The most significant factor in determining appropriate first-line treatment is accurate and reproducible prediction of a negative circumferential resection margin. MRI is quickly emerging as the gold standard for the preoperative staging of rectal cancer. It may be the key to assessing whether safe restorative resection is feasible or an abdominoperineal excision may be oncologically superior when performed in a more radical or cylindrical (extralevator) plane. This article explores the latest evidence for optimizing surgery in rectal cancer.     

Management and imaging of low rectal carcinoma

Large variations in recurrence rates have been reported with the best results following total mesorectal excision (TME) surgery for low and middle rectal cancers. However, the low rectal cancers still have higher rates of local recurrence (up to 30%) whether operated by low anterior resection or abdominoperineal excision (APE) due to high rates of circumferential margin involvement. The treatment of choice for low rectal cancers that encroach upon the potential circumferential resection margin is surgery combined with preoperative neoadjuvant treatment. Preoperative chemotherapy combined with long-term radiotherapy reduces recurrence rates and preoperative loco-regional staging can help to select the patients more likely to benefit from neo-adjuvant therapy. Surface coil MRI is the most promising modality for patient selection, which can provide good views of the circumferential resection margin especially the presence or absence of tumour encroaching the intersphincteric plane.     

Evolution of imaging in rectal cancer: multimodality imaging with MDCT,MRI, and PET

Magnetic resonance imaging (MRI), multidetector computed tomography (MDCT), and positron emission tomography (PET) are complementary imaging modalities in the preoperative staging of patients with rectal cancer, and each offers their own individual strengths and weaknesses. MRI is the best available radiologic modality for the local staging of rectal cancers, and can play an important role in accurately distinguishing which patients should receive preoperative chemoradiation prior to total mesorectal excision. Alternatively, both MDCT and PET are considered primary modalities when performing preoperative distant staging, but are limited in their ability to locally stage rectal malignancies. This review details the role of each of these three modalities in rectal cancer staging, and how the three imaging modalities can be used in conjunction.     

The importance of MRI for rectal cancer evaluation

Magnetic resonance imaging (MRI) has gained increasing importance in the management of rectal cancer over the last two decades. The role of MRI in patients with rectal cancer has expanded beyond the tumor-node-metastasis (TNM) system in both staging and restaging scenarios and has contributed to identifying “high” and “low” risk features that can be used to tailor and personalize patient treatment; for instance, selecting the patients for neoadjuvant chemoradiation (NCRT) before the total mesorectal excision (TME) surgery based on risk of recurrence. Among those features, the status of the circumferential resection margin (CRM), extramural vascular invasion (EMVI), and tumor deposits (TD) have stood out. Moreover, MRI also has played a role in surgical planning, especially when the tumor is located in the low rectum, when the relationship between tumor and the anal canal is important to choose the best surgical approach, and in cases of locally advanced or recurrent tumors invading adjacent pelvic organs that may require more complex surgeries such as pelvic exenteration. As approaches using organ preservation emerge, including transanal local excision and “watch-and-wait”, MRI may help in the patient selection for those treatments, follow up, and detection of tumor regrowth. Additionally, potential MRI-based prognostic and predictive biomarkers, such as quantitative and semi-quantitative metrics derived from functional sequences like diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE), and radiomics, are under investigation. This review provides an overview of the current role of MRI in rectal cancer in staging and restaging and highlights the main areas under investigation and future perspectives.     

Preoperative staging of rectal cancer

Detailed preoperative staging using high resolution magnetic resonance imaging (MRI) enables the selection of patients that require preoperative therapy for tumour regression. This information can be used to instigate neoadjuvant therapy in those patients with poor prognostic features prior to disturbing the tumour bed and potentially disseminating disease. The design of trials incorporating MR assessment of prognostic factors prior to therapy has been found to be of value in assessing treatment modalities and outcomes that are targeted to these preoperative prognostic subgroups and in providing a quantifiable assessment of the efficacy of particular chemoradiation treatment protocols by comparing pre-treatment MR staging with post therapy histology assessment. At present, we are focused on achieving clear surgical margins of excision (CRM) to avoid local recurrence. We recommend that all patients with rectal cancer should undergo pre-operative MRI staging. Of these, about half will have good prognosis features (T1-T3b, N0, EMVI negative, CRM clear) and may safely undergo primary total mesorectal excision. Of the remainder, those with threatened or involved margins will certainly benefit from pre-operative chemoradiotherapy with the aim of downstaging to permit safe surgical excision. In the future, our ability to recognise features predicting distant failure, such as extramural vascular invasion (EMVI) may be used to stratify patients for neo-adjuvant systemic chemotherapy in an effort to prevent distant relapse. The optimal pre-operative treatment regimes for these patients (radiotherapy alone, systemic chemotherapy alone or combination chemo-radiotherapy) is the subject of current and future trials.     

Rectal cancer staging: An up‐to‐date pictorial review

Colorectal cancer is the third most common malignancy worldwide, and rectal cancer (RC) accounts for 29% of all cases. Local staging of RC is crucial for the purposes of addressing patients appropriately to surgery alone or to preoperative chemoradiotherapy (pCRT) followed by total mesorectal excision (TME). Combined pCRT and TME may negatively affect rectal function, so rectum‐sparing approaches such as transanal local excision have been proposed as an alternative to TME for patients showing a major or complete clinical response on restaging after pCRT. Magnetic resonance imaging (MRI) has a fundamental role in the local staging and restaging of RC, with or without positron emission tomography (PET). PET/MRI enables a multiplanar high‐resolution morphological study of the pelvis, providing important information on cell density and metabolic activity with diffusion‐weighted imaging (DWI) and ¹⁸F fluorodeoxyglucose uptake respectively. This article offers a pictorial review of the MRI anatomy of the ano‐rectal region and an update on local RC staging with a hybrid ¹⁸F‐FDG PET/MRI scan.     

Radiothérapie préopératoire des cancers du rectum : volumes cibles

Preoperative radiochemotherapy followed by total mesorectal excision is the standard of care for T3-T4-N0 or TxN1 rectal cancer. Defining target volumes relies on the patterns of nodal and locoregional failures. The lower limit of the clinical target volume depends also on the type of surgery. Conformational radiotherapy with or without intensity-modulated radiotherapy implies an accurate definition of volumes and inherent margins in the context of mobile organs such as the upper rectum. Tumoral staging recently improved with newer imaging techniques such as MRI with or without USPIO and FDG-PET-CT. The role of PET-CT remains unclear despite encouraging results and MRI is a helpful tool for a reliable delineation of the gross tumour volume. Co-registration of such modalities with the planning CT may particularly guide radiation oncologists through the gross tumour volume delineation. Acute digestive toxicity can be reduced with intensity modulation radiation therapy. Different guidelines and CT-based atlas regarding the target volumes in rectal cancer give the radiation oncologist a lot of ground for reproducible contours.     

La radiothérapie des cancers du rectum : stratégie thérapeutique et perspective

Standard treatment consisting of chemoradiotherapy followed by radical surgery with total mesorectal excision, resulting in good oncologic local control but high morbidity and poor functional results. The same treatment applied to all patients presenting with low or mid T3–4 rectal tumors could result in overtreatment of small tumors. However, it remains insufficient (or unsatisfactory?) for locally advanced tumors regarding metastatic recurrence rate. Treatment is decided by a multidisciplinary board on the basis of initial staging, including MRI which allows for resection margin prediction and post-treatment response evaluation. The therapeutic strategy is changing towards upfront chemotherapy and therapeutic desescalation omitting radiotherapy or surgery in a rectal preservation strategy. Moreover, tumor response leads to new multidisciplinary board discussion and treatment adaptation.     

高分辨率磁共振成像在直肠癌术前评估中的应用价值

高分辨率磁共振成像（HR-MRI）已成为多学科团队（MDT）评估直肠癌不可或缺的影像学检查。高分辨率MRI可以对肿瘤进行准确的术前T、N分期和定位,同时准确评估肿瘤相关不良预后因素,包括环周切缘、脉管浸润、腔外侵犯深度和肛管周围组织受累程度等。准确的术前评估直接关系到直肠癌患者的治疗方案制定及手术方式的选择,对提高患者的预后和生命质量有重要的指导意义。     

中段直肠癌术前磁共振成像对术后复发及转移的预测价值研究

背景与目的：中段直肠癌根治性切除术后局部复发率和异时远处转移率较高,如果能够在术前筛选出术后局部复发及远处转移的高危人群,就有可能对高危人群进行针对性的系统治疗,改善患者预后。该研究旨在探讨中段直肠癌术前磁共振成像（magnetic resonance imaging,MRI）对术后局部复发及异时远处转移的预测价值。方法：回顾性分析哈尔滨医科大学附属肿瘤医院2013年3月—2014年12月经手术病理证实为直肠癌,并且术前MRI判断为中段直肠癌的患者278例,收集其MRI资料及随访资料,分析直肠癌术前MRI与术后局部复发及异时远处转移的相关性、直肠癌术后局部复发和异时远处转移的风险因素以及通过术前MRI预测直肠癌预后的价值。结果：278例患者中19例（6.83%）发生术后局部复发,42例（15.11%）发生异时远处转移。单因素分析结果表明,MRI评价T（mrT）分期（P＜0.001）、腹膜返折受侵（P＜0.001）与直肠癌术后局部复发具有相关性;mrT分期（P=0.013）、MRI评价N（mrN）分期（P＜0.001）、壁外血管侵犯（extramural vascular invasion,EMVI）（P＜0.001）、腹膜返折受侵（P＜0.001）与直肠癌异时远处转移具有相关性。逐步回归模型结果显示,腹膜返折受侵（P＜0.001）是直肠癌术后局部复发的重要风险因素;mrN1期（P=0.017）、mrN2期（P＜0.001）是直肠癌异时远处转移的重要风险因素。结论：直肠癌术前MRI能较好地预测术后局部复发和异时远处转移,有助于临床筛选高危患者,从而采取个性化治疗,以改善患者预后。     

MRI及DCE-MRI在直肠癌术前诊断及分期中的应用价值

目的探讨MRI及DCE—MRI在直肠癌术前诊断及分期中的应用价值。方法选择经肠镜活检确诊为直肠癌的患者32例,按照随机样本表法将患者分为2组,行MRI检查16例,行DCE—MRI检查16例,同时选择健康志愿者10名行常规盆腔DCE—MRI扫描作为对照。对比MRI及DCE—MRIT分期和N分期诊断差异,直肠癌病灶和直肠正常肠壁的TIC参数差异。结果MRI评价T分期有3例过高分期,2例过低分期,DCE—MRI有3例过高分期,1例过低分期,DCE—MRI对于T1-2、T3分期准确率高于MRI;MRI评价N分期有1例过高分期,4例过低分期,DCE—MRI有2例过高分期,2例过低分期,DCE—MRI对于N0、N1、N2分期准确率高于MRI（P〉0．05）。直肠癌病灶的SImin、SImax、SIR均高于直肠正常肠壁,而Tpeak小于直肠正常肠壁（P〈0．05）。结论MRI及DCE—MRI对直肠癌进行术前分期评价具有准确、系统、科学的特点,而DCE－MRI还能反映病灶局部的血液循环情况。     

The Importance of the Pathologist’s Role in Assessment of the Quality of the Mesorectum

Total mesorectal excision (TME) is considered standard of care for rectal cancer treatment. Failure to remove the mesorectal fat envelope entirely may explain part of observed local and distant recurrences. Several studies suggest quality of the mesorectum after TME surgery as determined by pathological evaluation may influence prognosis. We aimed to determine the prognostic value of the plane of surgery as well as factors influencing the likelihood of a high-quality specimen by reviewing the literature. A pooled meta-analysis of relevant outcome data was performed where appropriate. A muscularis propria resection plane was found to increase the risk of local recurrence (RR 2.72 [95 % CI 1.36 to 5.44]) and overall recurrence (RR 2.00 [95 % CI 1.17 to 3.42]) compared to an (intra)mesorectal plane. Plane of surgery is an important factor in rectal cancer treatment and the documentation by pathologists is essential for the improvement of TME quality and patient outcome.