Difference between revisions of "MRI of rectal cancer"

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=== Lymph nodes and tumour deposits ===
 
=== Lymph nodes and tumour deposits ===
* For nodal restaging the criteria described in Table 4 are recommended
+
Restaging after long course neoadjuvant treatment + downstaging interval
 +
 
 +
* Benign nodes: Short axis diameter <5 mm
 +
* Malign nodes: Short axis diameter ≥5 mm
  
 
=== Extramural vascular invasion ===
 
=== Extramural vascular invasion ===

Revision as of 22:51, 15 July 2019

Author: Rodrigo Horstmann Castilhos [notes 1]

This article is a summary of the Updated recommendations from the 2016 European Society of Gastrointestinal and Abdominal Radiology (ESGAR) to Magnetic resonance imaging for clinical management of rectal cancer.

MR image acquisition

Hardware

MRI (first choice)

  • Mandatory for both primary staging and restaging of rectal cancer.
  • Should use an external surface coil
  • 1.5T or 3.0T

Endorectal ultrasound (EUS)

  • Staging for early tumours considered for local excision
  • Superior diagnostic performance for differentiating T1 from T2 tumors

Patient preparation

  • Use of an enema is not routinely recommended
  • Use of spasmolytics may be useful to reduce bowel movement artefacts (no consensus: 57 % recommended/mandatory)
  • Use of endorectal filling is not routinely advised (no consensus: 71 % not recommended)

Sequences and sequence angulation

Sequences

  • A routine protocol should (at least) include:
    • 2D T2W sequences in 3 planes
    • DWI sequence (at least a high b-value of ≥800)
  • DWI images (including ADC maps) should mainly be assessed visually
    • Quantitative ADC measurements are not routinely advised
  • DWI is recommended for restaging of the yT-stage.
  • FS, T1W (non-enhanced and contrast-enhanced) and DCE sequences are not routinely recommended
  • Slice thickness ≤3 mm (axial and coronal T2W)

Sequence angulation

  • Transverse sequences: perpedicular to the rectal tumour axis
  • Coronal sequences: parallel to the rectal tumour axis
  • Coronal sequence parallel to the anal canal: should be included in distal tumours to assess the relation between tumour and anal sphincter

Patient preparation

Spasmolytics (optional)

  • Can be benefical for upper rectal tumors and when imaging is performed at 3.0T (bowel movement artifacts are most prevalent)

Endorectal filling (optional)

  • ~60 ml of gel (higher volumes compress perirectal tissues significantly)
  • Reduce susceptibility artefacts related to luminal gas on DWI.
  • Should not be used routinely: rectal wall distension may interfere with interpretation of the distance between the tumour and the mesorectal fascia, and high T2 signal of the gel may cause T2 shine through effects on DWI.

Structured reporting

Structured reporting is recommended and should include the items described in the report template of ESGAR.

Primary staging

Local tumour status

  • Morphology
  • Distance from the anorectal junction to the lower pole of the tumour
  • Tumour length
  • T-stage
  • Sphincter invasion

Tumour length

Although the panel agreed unanimously that ‘some measure of tumour size’ should be reported, there was no clear consensus on a specific metric, i.e. whether this should be one-dimensional, threedimensional or a volume measurement, and if and how after CRT an estimation of the tumour volume reduction should be provided. There is no solid evidence that favours one over another, although some authors have suggested that, specifically for assessment of chemoradiotherapeutic response, whole volume measurements may be preferable [23]. The panel acknowledges that several options exist but from a practical point of view decided to include tumour length as the main metric in the structured report template in Fig. 1, as this was deemed to be most commonly used and more practically applicable than other metrics, with good reported measurement reproducibility [20, 23, 24].

T-stage

  • MRI doesn't differentiate T1 from T2
  • T1-T2: limited to intestinal wall
    • Good prognosis
    • Rectal wall has an intact black line (outer muscle) surrounding the tumor
  • T3: extramural growth
    • T3a or T3b: ≤5 mm extramural growth
    • T3c or T3d: >5 mm extramural growth
  • T4

Observations:

  • Stranding into the mesorectal fat = equivocal sign; may indicate either a T2 or T3 tumour
  • The mesorectal fascia (MRF) is 'involved' if the distance between MRF and tumour is ≤1 mm
  • Stranding into the MRF = MRF is involved
  • Involvement of MRF = T3
  • Tumour invasion above the level of the peritoneal reflection (at the anterior side) should be considered at risk for peritoneal rather than MRF invasion
  • Invasion of the pelvic floor or pelvic side wall muscles = T4
  • Growth into the internal anal sphincter muscle = T3

Sphincter invasion

This information is relevant to surgical approach For low tumours with sphincter invasion, describe:

Depth of invasion

  • invades only the internal sphincter muscle
  • also involves the intersphincteric plane
  • also involves the external sphincter

Height of invasion

  • involves only the proximal 1/3 of the complex/anal canal
  • also involves the middle 1/3 of the complex/anal canal
  • also involves the lower 1/3 of the complex/anal canal
  • involves pelvic floor (levator)

Mesorectal fascia (and peritoneal) involvement

  • Shortest distance betwenn tumour and MRF
    • Free (>2 mm)
    • Threatened/involved (≤2 mm)
  • Location of the shortest distance between tumour and MRF
  • Tumour location in relation to anterior peritoneal reflection
    • below (MRF invasion)
    • above

The anterior peritoneal reflection is a landmark that is usually recognised easily on MRI and separates the intra- and extra-peritoneal portions of the mesorectal compartment [20]. Above the anterior peritoneal reflection, the mesorectal compartment is no longer enveloped by the mesorectal fascia on its anterior aspect. As such, anterior mesorectal fascia involvement should only be reported when below the level of the anterior peritoneal reflection.

Lymph nodes and tumour deposits

Extramural vascular invasion (EMVI)

  • Assessment of extramural vascular (or venous) invasion (EMVI) should be reported routinely, both for primary staging as well as for restaging after CRT.
  • EMVI is an important prognostic staging factor

Restaging after neoadjuvant treatment

  • Structured reporting is recommended
  • When considering organ preservation (watchful waiting) after CRT, MRI findings should be correlated with clinical examination (endoscopy / digital rectal examination)

Local tumour status

  • On T2-weighted MRI, a normalised, two-layered wall after CRT is suggestive of a complete response
  • On T2-weighted MRI, a completely hypointense (fibrotic) residue without an isointense mass indicates a complete or near-complete response

Mesorectal fascia (and peritoneal) involvement

  • If a fatpad re-appears between the tumour and MRF after CRT, the MRF should be considered uninvolved/cleared.
  • Persistent stranding of tumour into the MRF should be considered an equivocal sign that may or may not indicate persistent MRF involvement

Lymph nodes and tumour deposits

Restaging after long course neoadjuvant treatment + downstaging interval

  • Benign nodes: Short axis diameter <5 mm
  • Malign nodes: Short axis diameter ≥5 mm

Extramural vascular invasion

N staging

  • Important risk factor for local recurrence

Morphologically suspicious characteristics

  • Round shape
  • Irregular border
  • Heterogeneous signal

Malignant node criteria

  • Short axis diameter ≥9 mm
  • Short axis diameter 5-8 mm + ≥ 2 morphologically suspicious characteristics
  • Short axis diameter <5 mm + 3 morphologically suspicious characteristics
  • Mucinous lymph node (of any size)

N restaging

Treatment

Downloads

  • [1] Magnetic resonance imaging for clinical management of rectal cancer: Updated recommendations from the 2016 European Society of Gastrointestinal and Abdominal Radiology (ESGAR) consensus meeting

Notes

  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.

References


Beets-Tan RGH, Lambregts DMJ, Maas M, et al. Magnetic resonance imaging for clinical management of rectal cancer: Updated recommendations from the 2016 European Society of Gastrointestinal and Abdominal Radiology (ESGAR) consensus meeting [published correction appears in Eur Radiol. 2018 Jan 10;:]. Eur Radiol. 2018;28(4):1465–1475. doi:10.1007/s00330-017-5026-2