rectal ca

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Preoperative Staging for Rectal Cancer : MRI:

Preoperative Staging for Rectal Cancer : MRI Dr Nick Ferris Staff MRI Radiologist Western Hospital Footscray

MRI : strengths & weaknesses :

MRI : strengths & weaknesses High tissue contrast Multiplanar IV contrast not required Non-ionising : safe Spatial resolution < MDCT, EUS Anatomical information only * Slow, noisy Claustrophobia Exclusions – pacemakers, etc

MRI for Rectal Cancer Staging:

MRI for Rectal Cancer Staging 60 – 100 % accurate for T staging ~ 90 % accurate prediction of resection margin adequacy Up to 85 % sensitive for involved nodes M staging not usually attempted


Technique Hyoscine (Buscopan) No bowel prep, no IV contrast Survey sagittal, axial, +/- coronal T2 Thin oblique axial T2 Optional : T2 fat-suppressed, T1, contrast Research : perfusion, diffusion, spectroscopy, iron oxide

T staging:

T staging Relationship of tumour mass to rectal wall Mucosa & submucosa apparent thickness variable Muscularis propria variably low signal (T2)

T staging:

T staging Relationship of tumour mass to rectal wall T1 : Confined to mucosa/submucosa May be isointense T3 : Through muscularis propria Breach can be mimicked by desmoplastic reaction T4 : Into other organ, or through peritoneum Apposition does NOT = invasion T2 : Involves muscularis propria Muscularis signal variable

T staging:

T staging Relationship to meso-rectal fascia Sup. rectal vessels (& nodes) Pre-sacral fascia

Proven T1 lesion:

Proven T1 lesion

Proven T2 lesion:

Proven T2 lesion

Proven early (1 mm) T3 lesion:

Proven early (1 mm) T3 lesion

T3 at staging ; Proven T3 (after CRT):

T3 at staging ; Proven T3 (after CRT)

Presumed T4 lesion:

Presumed T4 lesion

Not an adenocarcinoma…:

Not an adenocarcinoma… Proven Gastro-Intestinal Stromal Tumour

Western Hospital T staging:

Western Hospital T staging Hist\MRI T0 T1 T2 T3 T4 T0 2 1 1 T1 1 1 T2 4 3 T3 1 4 T4 N = 18, all verified at histopathology of complete resection ; 61 % accurate

Western Hospital T Staging:

Western Hospital T Staging Hist\MRI T0 T1 T2/3 T3 T4 T0 2 2 T1 1 1 T2/3 10 T3 2 T4 N=18, all verified at histopathology of complete resection ; 83 % accurate

“T1/2” : early T3 at histopathology:

“T1/2” : early T3 at histopathology

“T2” : T1 at histopathology:

“T2” : T1 at histopathology

“T2” : dysplastic polyp at biopsy x 3:

“T2” : dysplastic polyp at biopsy x 3

“T2/3” : dysplastic polyp at biopsy:

“T2/3” : dysplastic polyp at biopsy

N staging:

N staging N1 : 1 – 3 regional nodes N2 : 4 or more regional nodes N3 : node along named vascular trunk, or apical node Most within 5 cm of primary

N staging:

N staging Size : 10 mm arbitrary & insensitive Contour : irregular * Signal pattern : heterogeneous * * Brown et al (2003) claim 85 % sensitivity / 97 % specificity Usually only pelvis assessed at MRI ? Future role for iron oxide

1 of 16 nodes positive…:

1 of 16 nodes positive…

Presumed N2/3 disease:

Presumed N2/3 disease

M staging:

M staging Not attempted at routine MRI, currently Routine rectal MRI not optimised for bone lesions (other sequences are very sensitive) Potentially : best test for liver metastases whole body staging MRI

What’s coming ?:

What’s coming ? Faster scans Tumour grading & monitoring : Apparent diffusion coefficient Perfusion indices Spectroscopy Iron oxide (USPIO) nodal contrast Whole body staging ? PET/MR


Conclusions… MRI is useful for initial T and N staging, but Less useful for early stage lesions (EUS) Current techniques not good at monitoring treatment response Watch this space !


References Beets-Tan RGH & Beets GL, Rectal Cancer : Review with Emphasis on MR Imaging. Radiology 232 : 335 – 346, 2004 Beets-Tan RGH, et al, Accuracy of magnetic resonance imaging in prediction of tumour-free resection margin in rectal cancer surgery. Lancet 357 :497-504, 2001 Brown G et al, Rectal Carcinoma : Thin-section MR Imaging for Staging in 28 Patients. Radiology 211 :215-222, 1999 Brown G et al, Morphologic Predictors of Lymph Node Status in Rectal Cancer with Use of High-Spatial-Resolution MR Imaging with Histopathologic Comparison, Radiology 227 :371-377, 2003 Brown G et al, High-Resolution MRI of the Anatomy Important in Total Mesorectal Excision of the Rectum, American Journal of Roentgenology 182 :431-439, 2004 Brown G et al, Effectiveness of preoperative staging in rectal cancer: digital rectal examination, endoluminal ultrasound or magnetic resonance imaging, Br J Cancer 91 :23-9, 2004

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