MRI of rectal cancer

From radlines.org
Jump to: navigation, search

Authors: Rodrigo Horstmann Castilhos; Authors of integrated Creative Commons article[1] [notes 1]

This article is a practical 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.

Planning

Choice of modality

  • MRI of rectal cancer is generally mandatory for both primary staging and restaging of a known rectal cancer.[1]
  • Endorectal ultrasound (EUS) is indicated for:[1]
  • Staging for early tumours considered for local excision
  • Superior diagnostic performance for differentiating T1 from T2 tumors

Hardware

  • Requires an external surface coil[1]
  • 1.5T or 3.0T.[1]

Patient preparation

  • Use of an enema is not routinely recommended[1]

Spasmolytics (optional)[1]

  • may be useful to reduce bowel movement artefacts (no consensus: 57 % recommended/mandatory)
  • Can be benefical for upper rectal tumors and when imaging is performed at 3.0T (bowel movement artifacts are most prevalent)

Endorectal filling (optional)[1]

  • Not routinely advised (no consensus: 71 % not recommended)
  • ~60 ml of gel (higher volumes compress perirectal tissues significantly)
  • Reduces 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.

Sequences and sequence angulation

Sequences[1]

  • A routine protocol should (at least) include:
    • 2D T2W sequences in 3 planes
    • DWI sequence (at least a high b-value of ≥800)
  • DWI and ADC maps should be assessed visually (not quantitatively)
  • 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

All tumours:[1]

  • Transverse sequences: perpedicular to the rectal tumour axis
  • Coronal sequences: parallel to the rectal tumour axis

Distal tumours:[1]

  • Include coronal sequence parallel to the anal canal to assess the relation between tumour and anal sphincter

Structured reporting

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

See also: General notes on reporting

Primary staging

Local tumour status

Morphology

Morphology[1]

  • Solid - polypoid
  • Solid - (semi-)annular
  • Mucinous

Circunferential location within the rectal wall[1]

  • e.g. from X to X o'clock
  • Should routinely be reported

Distance from anorectal junction

  • Distance from the anorectal junction to the lower pole of the tumour[1]

Tumour length

There is agreement 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. 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.[1]

T-stage

  • MRI doesn't differentiate T1 from T2[1]
  • T1-T2: limited to intestinal wall[1]
  • T3: extramural growth (including growth into the internal anal sphincter muscle)[1]
    • T3a or T3b: ≤5 mm extramural growth[1]
    • T3c or T3d: >5 mm extramural growth[1]
  • T4[1]
    • T4a: Invasion of peritoneal reflection
    • T4b: Invasion of surrounding organs

Observations:[1]

  • Stranding into mesorectal fat = equivocal sign; may indicate either a T2 or T3 tumour
  • 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[1]

For low tumours with sphincter invasion, describe:[1]

Depth of invasion[1]

  • invades only the internal sphincter muscle (T3)
  • also involves the intersphincteric plane
  • also involves the external sphincter

Height of invasion[1]

  • 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[1]
    • Free (>2 mm)
    • Threatened/involved (≤2 mm)
  • Location of the shortest distance between tumour and MRF[1]
  • Tumour location in relation to anterior peritoneal reflection[1]
    • below: MRF invasion
    • above: when on anterior side = at risk for peritoneal invasion (rather than MRF invasion)

Observations:[1]

  • 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. 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.
  • Mesorectal fascia involvement:
    • Shortest distance between tumour and MRF
      • Free: >2 mm
      • Threatened: 1.1-2 mm
      • Involved (=T3): ≤1 mm or stranding into the MRF

Lymph nodes and tumour deposits

  • Important risk factor for local recurrence[1]

Morphologically suspicious characteristics[1]

  • Round shape
  • Irregular border
  • Heterogeneous signal

Malignant node criteria[1]

  • 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)

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.[1]
  • EMVI is an important prognostic staging factor[1]

Restaging after neoadjuvant treatment

  • Structured reporting is recommended[1]
  • When considering organ preservation (watchful waiting) after CRT, MRI findings should be correlated with clinical examination (endoscopy / digital rectal examination)[1]

Local tumour status

T2W[1]

  • No residual tumour mass
    • Complete response: a normalised, two-layered rectal wall
    • Complete or near-complete response: a completely hypointense residue (fibrotic wall thickening) without clear residual isointense mass
  • Residual tumour mass (and/or focal high sinal on DWI)
    • yT-stage: yT1-2
    • yT3
      • yT3a or yT3b (≤5 mm extramural growth)
      • yT3c or yT3d (>5 mm extramural growth)
    • yT4, based on growth into:
  • Distance from the anorectal junction to the lower pole of the tumour (in cm)[1]
  • Tumour length (in cm)[1]
  • Sphincter invasion[1]

For low tumours with sphincter invasion, describe:[1]

Depth of invasion[1]

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

Height of invasion[1]

  • 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

  • If a fatpad re-appears between the tumour and MRF after CRT, the MRF should be considered uninvolved/cleared.[1]
  • Persistent stranding of tumour into the MRF should be considered an equivocal sign that may or may not indicate persistent MRF involvement[1]

Lymph nodes and tumour deposits

Restaging after long course neoadjuvant treatment + downstaging interval[1]

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

Extramural vascular invasion

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

  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 1.26 1.27 1.28 1.29 1.30 1.31 1.32 1.33 1.34 1.35 1.36 1.37 1.38 1.39 1.40 1.41 1.42 1.43 1.44 1.45 1.46 Beets-Tan, Regina G. H.; Lambregts, Doenja M. J.; Maas, Monique; Bipat, Shandra; Barbaro, Brunella; Curvo-Semedo, Luís; Fenlon, Helen M.; Gollub, Marc J.; et al. (2017). "Magnetic resonance imaging for clinical management of rectal cancer: Updated recommendations from the 2016 European Society of Gastrointestinal and Abdominal Radiology (ESGAR) consensus meeting ". European Radiology 28 (4): 1465–1475. doi:10.1007/s00330-017-5026-2. ISSN 0938-7994.