MRI in the Staging of Rectal Cancerg g

Kartik S Jhaveri, MDAbdominal ImagingAssistant Professor Faculty of MedicineAssistant Professor, Faculty of Medicinekartik.jhaveri@uhn.on.ca

ObjectivesWhy MRI ?Normal MR AnatomyNormal MR AnatomyPreoperative StagingTTNM

• Post Treatment and Recurrence Evaluation• Conclusion

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Staging

ERUS

MRI PET-CTMRI

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Endorectal US(ERUS) has high accuracyaccuracy

So Why MRI…….?y

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Limitations of ERUS MRI

Small or Very large tumors Very High or Very Low MassSt ti CStenotic CancerMesorectal FasciaLN detection < MRILN detection < MRI

MRI is also performed sans ER device

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ERUS VS MRIT1 VS T2 ERUS

MST2 VS T3 MRI > ERUS

MT

T3 VS T4 MRI >ERUS RA

GN MRI >ERUS I

G

E

M CT/PET CT6

M CT/PET-CT

What About CT ?What About CT ?

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CT VS MRICT =Inferior Contrast Resolution

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NORMAL MRI ANATOMY

T2 AxialT2 Axial Inner High Signal -Mucosa/Submucosa

Middle Low Signal –

Muscularis Propria

Outer High Signal –

Mesorectal Fat

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T2 CORONAL

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T2 SAGITTAL

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MESORECTAL FASCIA

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ROLE OF HIGH RESOLUTION MRIPre-operative road map of tumor

T stage ( 2 , 3 OR 4)CRM (Circumferential resection margin)Di t f l / hi tDistance from anal verge/sphincter

• Define Prognostic groups• Define Prognostic groups

Deciding Preoperative therapyg p pyLocal Recurrence Risk

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ManagementT1 Transanal ExcisionT2T3

TMEPreop Chemorad + TMET3 Preop Chemorad TME

vs

T4TME + Postop Chemorad

• Preop Chemorad +ExenterationT4 Preop Chemorad Exenteration

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MRI AccuracyT Staging : 71-91 %N Staging : 43-85 %CRM 95 %CRM : 95 %Highest Accuracy and Consistency g y y

Beets-Tan RG et al. Lancet 2001Brown G et al. BJS 2003 & RSNA 2004 Nagtegaal I et al Am J Surg Path 2002

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Nagtegaal I et al. Am J Surg Path 2002

T Stageg

T1 s carcinoma in situT1 invades sub-mucosaT1 invades sub mucosaT2 invasion of circular/longitudinal layerslayersT3 invasion through muscularis T4 direct invasion of other organs orT4 direct invasion of other organs or visceral peritoneum

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T1

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T2

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T3

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T3Ci f i l R i M i CRMCircumferential Resection Margin =CRM

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CRM and MRIMRI : >6mm from CRM

P th l 2 N ti M iPathology >2mm Negative Margin

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Good and Bad T3

CRM >6 CRM 022

CRM >6mm CRM = 0 mm

T4

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T4

24Pre sacral infiltration

MRI PITFALLS IN T STAGET1 VS T2

T3 –DESMOPLASTIC REACTION-OVERSTAGINGOVERSTAGING

CRM Thin PatientsCRM -Thin Patients- Anterior wall tumor- Lower rectal tumor

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T1 OR T2

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T3 OVERSTAGING

Desmoplastic Reaction

RadioGraphics 2006; 26:701–714

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CRM

LOW AND ANTERIOR TUMOR28

LOW AND ANTERIOR TUMOR

N STAGEN0: No regional lymph node metastasis

N1: Metastases in1 to 3nearby lymph nodes

N2: Metastases in 4 or more nearby lymph nodesy y p

N3 : Distant LNRectum : External &CommonRectum : External &Common iliac and abdominal

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Criteria of nodal metastasis

Size : >8mm and round > 10mm in short axis and oval

Border : Spiculated or indistinctBorder : Spiculated or indistinct

Signal intensity

Enhancement pattern

Moderate accuracy, sensitivity and specificity !!!

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N STAGE

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Nanoparticle Enhanced MR –Nodal stagingNodal staging

USPIOUSPIO

NEJM . Harisinghani et al. 348 (25): 2491

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USPIO

BENIGN

MALIGNANT

33 Courtesy. Dr Harisinghani ,MGH

USPIO-enhanced MR Imaging for Nodal Staging in Patients with Primary Rectal Cancer.

Max J. Lahaye et al Radiology: 246: Number 3,March 2008

Short axis <10mm

Sensitivity 93%

Specificity 96%p y

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N-stage: PET/CT

Accuracy upto 80%Advantage of PET: Identification of sub-centimeter, metastatic nodes.

Disadvantage of PET: cannot detect small volume disease within nodes (microscopic metastases).

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Response Assessment To Ch R dChemoRads

MRIMRIDiffusion Weighted MRI (DWI)

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MRI

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MRI-CONTRAST

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Diffusion Weighted Imaging-DWIDWI is a recently introduced technique that depicts differences in molecular diffusion caused by thediffusion caused by the random and microscopic motion of molecules, which is known as Brownian motion

• Restricted Diffusion results in higher signal on DW image (EPI)-more typical of malignant tissueg

May have role for assessing or predicting treatmentor predicting treatment response by ADC calculation

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DWI-Rectal Cancer

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Recurrent Tumor Evaluation

Sagittal plane essential when assessing g p gsacral involvement

Recurrence often nodular in morphology

Post treatment fibrosis often co-exists

MRI or PET ?

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Recurrent tumorRecurrent tumor

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Recurrent tumorRecurrent tumor

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PET

P APR B i l B f hPost APR. Benign presacral mass: Bx of the mass was negative.

Malignant presacral tissue.45

g pAccuracy in high 90% for PET-CT

Intriguing Case

RECURRENCE ?

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CHRONIC SINUS TRACT OR RECURRENCERECURRENCE

2007

2008

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ConclusionEndorectal US for T1 VS T2MRI FOR Stage T3 and HigherMRI for CRM-Tumor distanceLower Accuracy for Nodal Staging? USPIO in future? USPIO in future

• PET-CT for Tumor recurrence in uncertain casesuncertain cases

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