The aims of our poster are:
-to review the MRI technique and protocol in preoperative local staging of rectal cancer (RC);
-to identify radiological signs that are useful for both the clinician and the surgeon;
-to provide some “tips & tricks” in the radiological evaluation of MR images in RC staging

AMICO, Maria

GALFANO, Maria Cristina

Lo Re, G.

PERI, Mariangela

PICONE, Dario

RABITA, Fabrizio

SALERNO, Sergio

VERNUCCIO, Federica

Archivio istituzionale della ricerca - Università di Palermo

Page 1 of 14Preoperative assessment of rectal cancer: an accurate MRIprotocol a radiological templatePoster No.: C-1503Congress: ECR 2015Type: Educational ExhibitAuthors: F. Rabita, D. Picone, F. Vernuccio, M. C. Galfano, M. Amico, M.Peri, G. Lo Re, S. Salerno; Palermo/ITKeywords: Gastrointestinal tract, Abdomen, Oncology, MR, Staging,Education and training, NeoplasiaDOI: 10.1594/ecr2015/C-1503Any information contained in this pdf file is automatically generated from digital materialsubmitted to EPOS by third parties in the form of scientific presentations. Referencesto any names, marks, products, or services of third parties or hypertext links to third-party sites or information are provided solely as a convenience to you and do not inany way constitute or imply ECR's endorsement, sponsorship or recommendation of thethird party, information, product or service. ECR is not responsible for the content ofthese pages and does not make any representations regarding the content or accuracyof material in this file.As per copyright regulations, any unauthorised use of the material or parts thereof aswell as commercial reproduction or multiple distribution by any traditional or electronicallybased reproduction/publication method ist strictly prohibited.You agree to defend, indemnify, and hold ECR harmless from and against any and allclaims, damages, costs, and expenses, including attorneys' fees, arising from or relatedto your use of these pages.Please note: Links to movies, ppt slideshows and any other multimedia files are notavailable in the pdf version of presentations.www.myESR.orgPage 2 of 14Learning objectivesThe aims of our poster are:-to review the MRI technique and protocol in preoperative local staging of rectal cancer(RC);-to identify radiological signs that are useful for both the clinician and the surgeon;-to provide some "tips & tricks" in the radiological evaluation of MR images in RC staging.BackgroundColorectal cancers are the second most frequent tumours in Western countries,particularly 1/3 of these cancers are localized in the rectum.Surgery provides a wide range, from the trans-anal resection to multiorgan excision,remains the best therapeutic choice. However, nowadays, the concept of "mesorectalexcision" is widely accepted among surgeons being supported by a low risk of localrecurrence and a good compliance by patients. Hence, the need for a multidisciplinaryapproach, which includes oncologists, surgeons, radiologists and radiotherapists, eachplaying a key role in the management of patients with RC.MRI is a valuable diagnostic tool to carry out a correct preoperative local stagingof the disease and identify patients in need of a chemoradiotherapy (CRT) adjuvantpreoperative or even identify cases where this proves simply a therapeutic overtreatment.Partly following the numerous scientific guidelines on the MR-staging of the CR andsupported by our personal and validated daily experiences , we aim to offer readers "anaccurate MRI protocol and a radiological template".Findings and procedure detailsOur educational exhibit focuses exclusively on the preoperative evaluation of patientswith CR. However, the MRI protocol described below is applicable both in the first stagingPage 3 of 14and in the restaging after adjuvant chemoradiotherapy, but MRI parameters useful in thislatter situation will not be described.PATIENT PREPARATION- Although some guidelines do not recommend routine endorectal filling, we recommenda rectal relaxation through about 60-100 ml of a semiliquid solution containing ultrasoundgel and water, administered by endorectal small cannula.TIPS & TRICKS: you should advise patients to make two small evacuation enemas(e.g. through glycerine), respectively the night before and the morning of the MRIexamination;you should not stretch too much the rectal ampulla since it could distort themorphology of the tumor, smashing it too much on the rectal wall and in rare cases youwill make a compressive effect on mesorectal fat.- Administration of a spasmolytic agent before image acquisition to reduce bowel motionartifacts.TIPS & TRICKS: if you made rectal distension, the spasmolytic agent helps the patientto maintain continence during MRI examination.MRI ACQUISITION PROTOCOL:- Use of high field MRI equipment (at least 1.5 Tesla MR scanner).- Use phased array surface coil; endorectal coil is not recommended, especially inpatients with stenosing tumor.- Patient in the supine position.- Average MR duration: about 30 minutes.Below the MRI sequences we use in our clinical practice, listed in temporal order; howeverare dutiful some premises:• except for some post-contrastographic imaging and functional studies (DWIand Dynamic Contrast-Enhanced-DCE), in the morphological evaluation ofthe CR by sequences turbo spin echo (TSE) sequences, must not be usedfat suppressed sequences (FAT-SAT);• slice thickness must be in a range of about 1-4 mm;MR images acquisition includes sequences acquired before and after contrast mediuminjection:Page 4 of 14- PRE-CONTRASTOGRAPHIC SEQUENCES1. sagittal TSE-T2 weighted: it must be the first acquired sequence: it will constitute areference for the following axial and coronal oblique images (see below);2. axial TSE-T2 weighted: includes the whole pelvis; it shows a panoramic view of thelower abdomen, including the tumor, extramesorectal and any peritoneal nodes;3. axial TSE- T1 weighted: same as above but T1 weighted;4. DWI free-breathing technique and multi b-values (0, 500, 1000 s/mm2) in the axialplane: quantitative and qualitative evaluation of the tumor.The hyperintense signal in DWI reflects a high tumor cellularity, intratumoral edema andany possible intralesional cystic component, which is typical in the mucinous variant ofthe CR (Fig.3-left). Moreover, it allows calculating ADC values which are predictive ofa possible neoadjuvant therapy success. Many studies, indeed, have shows that someCR with low-baseline pretreatment ADC values responded better to chemotherapy orradiation treatment than tumors with high-pretreatment ADC values. However, there isnot any standardized cut-off value.TIPS & TRICKS: DWI allows better visualizing even small tumors and identifying, but notcharacterizing, peritumoral nodes. The use of high b-values (e.g. 1000 s/mm2) eliminatesthe high signal due to the ultrasound gel used for endorectal filling, showing only therestriction in the signal of the tumor. You should calculate ADC values not just on a smalltumor volume, but on a wide area (ROI) manually drawn that includes the tumor itself,thus increasing the diagnostic accuracy.5. oblique axial plane High resolution (HR) TSE T2 weighted: using as reference imageof the TSE-T2 weighted image in the sagittal plane, you have to consider a plane whichis perpendicular to the major axis of the tumor. This is the key sequences of the wholeMRI protocol: since it defines the exact relationship of the tumor to the mesorectal fatand mesorectal fascia.TIPS & TRICKS: pretend to have images free from motion artifacts. If tumor is verywide in length with a curved major axis, you have make a second acquisition using aperpendicular plane which is slightly modified, and then choose which one best describesthe relationship with the mesorectal fascia.6. coronal oblique HR TSE T2 weighted: using as reference image sagittal T2 weightedsequence, you have to create a plane which is parallel to the anal canal. This sequenceis useful in evaluation of sphincter involvement in "low" RC.Page 5 of 14TIPS & TRICKS: these two sequences (axial and coronal oblique) are acquired using anarrow (16 cm) Field of View (FOV) targeted exclusively to mesorectal region. In axialand coronal oblique sequences we do not use pre-saturation bands- POST-CONTRASTOGRAPHIC SEQUENCES1. DCE-MRI Fat-sat in the axial plane: the perfusion studies allow estimating tumorneoangiognenesis and predicting response to chemotherapy. Furthermore, together withDWI sequences, they allow differential diagnosis, in the assessments after adjuvanttherapy, including fibrosis and tumor recurrence.TIPS & TRICKS:although not being standardized, we consider necessary to performperfusion studies to best validate the technique trying to MR- staging not only throughmorphological parameters but also with functional ones. Considering that in the protocolintravenous contrast medium is injected it would be inappropriate if perfusion study werenot performed.2. axial and sagittal TSE T1 weighted: morphological post-contrastographic evaluation.3. High-resolution volumetric 3D fat-sat T1 weighted: it provides an excellent post-contrast enhancement morphological evaluation of the tumor (Fig.2-right and Fig.3-right)and, in some cases, it is useful in identifying the venous peritumoral spreading.IMAGES ANALYSISHere are parameters that should be evaluated and included in our suggested radiologicaltemplate, reporting only "WHAT surgeons, oncologist and radiotherapist WANT"1. Locate tumor: "Where is the tumor?"- Measure the distance from the anal margin to lower border of the tumor:• < 5cm: lower III of the rectum (low rectal);• between 5-10cm: medium III of the rectum (mid rectal);• > 10 cm: upper III of the rectum (high rectal);TIPS & TRICKS: tumors of the upper rectum easily spread in the peritoneum; this lattercovers only the anterior wall of the rectum. The tumors of the low rectum tend to recurmore.- Craniocaudal extension of the tumor (measured in centimetres).- Distance between anal verge and upper border of the tumor.Page 6 of 142. Depth of invasion through the layers of the intestinal wall and in the surroundingMesorectal fat: " What is the tumor spread?"-T staging: the process of T-Staging is shown in the Table 1 and Fig.1.MRI helps to distinguishing the different layers of the bowel: in T2 weighted images, thesubmucosa has an high signal intensity, the muscolaris has a low signal intensity, whilethe perirectal fat has an high signal intensity and contains signal void vessels.TIPS & TRICKS: Do this assessment just on HR T2 weighted sequences in theaxial oblique plane (Fig. 2-left). T1 and T2 tumors can not be distinguished throughMRI, endoanal ultrasound must be used in these cases. You will often find somedifficulties in tumors with minimal mesorectal spread (T3a, T3b), because aroundthe rectal wall there can be present a desmoplastic stromal reaction, which can bemisinterpreted as tumor tissue. Hence, we advise to use these criteria: appearance with"spiculated" striae represents a desmoplastic fibrotic reaction, while the presence of"broad based" or nodular tissue permeating into the mesorectal fat and in continuity withthe intramural portion of the tumor is indicative of neoplastic spread. Remember thatthe distinction between T2 and T3 with mesorectal invasion less than 5 mm (T3a andT3b) may be irrelevant, as these types of cancer may not benefit from some adjuvantchemoradiotherapy.- Growth pattern: annular, polypoid , ulcerated , mixed.- Sfinterial staging : in cases of " low" rectal cancer it is useful to carry out a tumor stagingconsidering the sphincter structures (see Table 2 and Fig.4). Use the coronal obliqueplane HR T2 weighted sequences.3. Involvement of mesorectal fascia: "What is the status of Mesorectal Fascia?"- Evidence of direct infiltration of the mesorectal fascia by the tumor or nodes: yes or no- Circumferential Resection Margin (CRM) status: shortest distance from the tumor in themesorectal fat to the mesorectal fascia (measured in millimetres):• > 1 mm: CRM negative• < 1 mm: CRM positiveTIPS & TRICKS: the presence of a node distant less than 1 mm from the mesorectalfascia is predictive of infiltration (CRM positive; see later).4. NODAL STATUS: " What is the nodal involvment?"Page 7 of 14- N-stage: number of probably metastatic nodes within the mesorectal fat:• N0: no nodes• N1: 1-3 nodes• N2: >4 nodesCriteria of malignancy: size> 8 mm; round shape with a short axis diameter > 5 mm;irregularity of the surrounding capsule; irregular and spiculates borders; inhomogeneousintensity signal MRI (likely contain areas of necrosis or mucin); the presence of intranodalfat is not a typical feature of mesorectal nodes. Post-contrastographic enhancement ispresent in both hyperplastic and metastatic nodes.- Node at <1 mm of distance from mesorectal fascia: CRM+- Extramesorectal nodes: located in the pelvis (iliac, obturator, etc)TIPS & TRICKS: The nodal involvement is defined with certainty only throughhistopathology; MRI alone is not sufficient due to the presence (not uncommon) ofmicrometastases. Use caution in their assessment; remember that the nodal spread isone of the most important risk factors both for local and distant recurrence. The DWIevaluation does not increase the specificity. Both malignant and benign nodes showshigh signal on DWI images. Use however this sequence to facilitate their detection(especially for small nodes). The ADC of metastatic nodes is usually lower, but it is notyet estabilished a reference cut-off. Currently you can not use it as a diagnostic criterion.5. Negative prognostic factors associated: "There are more poor prognostic factors?- Extramural vascular Invasion (EMVI): the presence of venous vascular spread isindicative of probable relapse and/or high malignancy. Diagnostic criteria EMVI: proximitybetween tumor and vascular structures; rounded edges of the vessels, swollen andwiden appearance (presence of intraluminal tumor tissue, neoplastic thrombosis) andinhomogeneous signal intensity (reduced artefact flow void)TIPS & TRICKS: do not confuse EMVI with peritumoral desmoplastic reaction (spiculatedand thin appearance)- Presence of intratumoral mucin pool: hyperintense foci on T2w sequences, indicativeof mucin pool.TIPS & TRICKS: The mucinous variant of CR is correlated with increased localrecurrence, nodal and peritoneal spread. Intratumoral necrosis or abscesses can mimicmucin pool. Medium signal intensity in FatSat T2w images and intravenous administrationPage 8 of 14of gadolinium can help: in some cases, mucin shows a rise of intensity signal in post-contrastographic sequences.- Pelvic secondary nodulations: peritoneal metastatic nodules, with spiculated andirregular margins that show inhomogeneous post-contrastographic enhancement (tumorlike).- Dynamic perfusional evaluation:• Wash-in and Wash-out curves: in our experience the neoplastic tissue(compared to healthy rectal wall) has a significant and rapid wash-in withmoderate plateau phase and/or mild wash-out.• K-trans: the presence of high values of K-trans in the context of the tumortissue, compared to normal rectal wall, is indicative of neoplasia.TIPS & TRICKS: although still under study, perfusion imaging is used as tool forassessing angiogenesis and thus the possibility of CRT success. Rectal tumors withhigher permeability at presentation appear to respond better to CRT than those oflower permeability. Ongoing studies are evaluating its usefulness in the responseto neoadjuvant treatment (in combination with assessment DWI) with the ability todiscriminate the residual tumor from fibrosis.Images for this section:Page 9 of 14Table 1: T-StagingTable 2: Sfinterial Staging (for "low" rectal cancerPage 10 of 14Fig. 1: T-StagingPage 11 of 14Fig. 2: MRI study shows mid-rectal cancer, mesorectal spread(T3), inhomogeneouscontrast enhancement and moderate vascular spreading.Fig. 3: MRI study shows mid-Low rectal cancer with inhomogeneous contrastenhancement, vascular spreading, high restriction in DWI sequence and presence ofmetastatic lymph node close to mesorectal fascia.Page 12 of 14Fig. 4: Sfinterial StagingPage 13 of 14ConclusionLocal staging of rectal cancer through MRI plays a key role in patient's therapeuticmanagement, reducing the risk for local recurrence or distal spread and helps topreoperatively identify valuable prognostic information. MRI report must be focused toprovide clear, detailed and above all "necessary" data to the multi-disciplinary team(oncologist, radiotherapist, surgeons) involved in the management of the patient. Eachof them would love to get from radiologist comprehensive and exhaustive local stagingin order to draw up a proper therapeutic planning of each patient with RC.Personal informationReferences-Barbaro B, Vitale R, Leccisotti L et-al. Restaging locally advanced rectal cancer with MRimaging after chemoradiation therapy. Radiographics. 2010;30 (3): 699-716-Beets-Tan RG, Lambregts DM. Magnetic resonance imaging for the clinicalmanagement of rectal cancer patients: recommendations from the 2012 EuropeanSociety of Gastrointestinal and Abdominal Radiology (ESGAR) consensus meeting. Eur.Radiol 2013 Sep;23(9):2522-31.-Brown G, Richards CJ, Bourne MW et al (2003)Morphologic predictors of lymph nodestatus in rectal cancer with use of high-spatial-resolution MR imaging with histopathologiccomparison. Radiology 227(2):371-377-DeVries AF, Kremser C, Hein PA et al (2003) Tumor microcirculation and diffusionpredict therapy outcome for primary rectal carcinoma. Int J Radiat Oncol Biol Phys 56:958-965-Dzik-Jurasz A, Domenig C, George M et al (2002) Diffusion MRI for prediction ofresponse of rectal cancer to chemoradiation. Lancet 360:307-308-Hussain SM, Outwater EK, Siegelman ES (1999) Mucinous versus non-mucinous rectalcarcinomas: differentiation with MR imaging. Radiology 213:79-85Page 14 of 14-Yeo, D.-M., Oh, S. N., Jung, C.-K., Lee, M. A., Oh, S. T., Rha, S. E., Jung, S. E., Byun, J.Y., Gall, P. and Son, Y. (2013), Correlation of dynamic contrast-enhanced MRI perfusionparameters with angiogenesis and biologic aggressiveness of rectal cancer: Preliminaryresults. J. Magn. Reson. Imaging-Kim MJ, Park JS, Park SI et al (2003) Accuray in differentiation of mucinous andnonmucinous rectal carcinoma on MR imaging. J Comput Assist Tomogr 27:48-55-Kim JH, Beets GL, Kim MJ et al (2004) High-resolution MR imaging for nodal staging inrectal cancer: are there any criteria in addition to the size? Eur J Radiol 52(1):78-83-Kim NK, Kim MJ, Park JK et al (2000) Preoperative staging ofrectal cancer with MRI:accuracy and clinical usefulness. Ann Surg Oncol 7:732-737-Koh DM, Collins DJ (2007) Diffusion-weighted MRI in the body: applications andchallenges in oncology. AJR Am J Roentgenol 188:1622 1635-Schäfer, A.-O., & Langer, M. (2010). MRI of rectal cancer: Clinical atlas. Berlin: Springer-Verlag-Smith NJ, Shihab O, Arnaout A et al (2008a) MRI for detection of extramural vascularinvasion in rectal cancer. AJR Am J Roentgenol 191:1517-1522-Taylor FG, Swift RI, Blomqvist L et al. A systematic approach to the interpretation ofpreoperative staging MRI for rectal cancer. AJR Am J Roentgenol. 2008;191 (6): 1827-35-Valentini V, Cellini F, Barba MC, et al. (2012) Multidisciplinary Management of RectalCancer Questions and Answers. Berlin: Springer-Verlag.

PREOPERATIVE ASSESSMENT OF RECTAL CANCER: AN ACCURATE MRI PROTOCOL A RADIOLOGICAL TEMPLATE

https://iris.unipa.it/retrieve/handle/10447/120812/180141/ECR2015_C-1503.pdf

PREOPERATIVE ASSESSMENT OF RECTAL CANCER: AN ACCURATE MRI PROTOCOL A RADIOLOGICAL TEMPLATE

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Archivio istituzionale della ricerca - Università di Palermo