Revision 39 for 'Rectal cancer (staging)'

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Rectal cancer (staging)

Staging strongly influences the success of, and rate of local recurrence following rectal cancer resection. MRI is the modality of choice for the staging of rectal cancer, to guide surgical and non-surgical management options. MRI is used at diagnosis, following downstaging chemoradiotherapy, and in follow-up, if a non-operative approach is used,


TNM staging

See: TNM staging system for a general description.

Primary tumor staging (T)

Strictly speaking TMN staging, such as American Joint Committee on Cancer (AJCC) 8th edition, does not sub-classify T3. However, this sub-classification does have treatment and prognostic significance 7,8

  • Tx: primary tumor cannot be assessed
  • T0: no evidence of primary tumor
  • Tis: carcinoma in situ: intraepithelial or invasion of lamina propria
  • T1: tumor invades submucosa
  • T2: tumor invades muscularis propria
  • T3: tumor invades through the muscularis propria into the subserosa or into non-peritonealised perirectal tissues
    • T3a: tumor extends <1 mm beyond muscularis propria 4
    • T3b: tumor extends 1-5 mm beyond muscularis propria 4
    • T3c: tumor extends 5-15 mm beyond muscularis propria 4
    • T3d: tumor extends 15 mm beyond muscularis propria 4
  • T4: tumor invades directly into other organs or structures and/or perforates visceral peritoneum
    • T4a: tumor penetrates to the surface of the visceral peritoneum
    • T4b: tumor directly invades or is adherent to other organs or structures
Regional lymph nodes (N)

Signal heteroegenity and irregular contour are the most reliable signs of nodal involvement on MRI.

  • Nx: regional nodes cannot be assessed
  • N0: no regional lymph node metastases
  • N1: metastasis in 1-3 regional (peri-rectal) lymph nodes
    • N1a: metastasis in 1 regional lymph node
    • N1b: metastasis in 2-3 regional lymph nodes
    • N1c: tumor deposit(s) in the subserosa, mesentery, or nonperitonealized pericolic or perirectal tissues without regional nodal metastasis
  • N2: metastasis in 4 or more regional lymph nodes
    • N2a: metastasis in 4-6 regional lymph nodes
    • N2b: metastasis in 7 or more regional lymph nodes
Metastases (M)
  • Mx: cannot be assessed
  • M0: no distant metastasis
  • M1: distant metastasis
    • M1a: metastasis confined to one organ or site (for example, liver, lung, ovary, nonregional node)
    • M1b: metastases in more than one organ/site or the peritoneum
Stage groupings
  • stage 0: Tis N0 M0
  • stage I: T1-2, N0 M0
  • stage II
    • IIa: T3, N0, M0
    • IIb: T4a, N0, M0
    • IIc: T4b, N0, M0
  • stage III
    • IIIa: T1-2, N1, M0
    • IIIb: T3-4, N1, M0
    • IIIc: T3-4b, N2, M0
  • stage IV: any T, any N M1
Additional prognostic indicators

The following are significant prognostic indicators, and should be commented on when staging rectal cancer with MRI, alongside the TNM stage:

  • extramural venous invasion (EMVI)
    • may be contiguous or non-contiguous
    • non-contiguous deposits reflect N1c
    • imparts poor prognosis as a predictor of haematogenous spread
  • circumferential resection margin (CRM)
    • represented by the mesorectal fascia (MRF)
    • CRM positive if either tumor, involved lymph node, or EMVI (continuous or discontinuous) is within 1mm of the mesorectal fascia
    • peritoneal reflection does not constitute CRM, which if involved reflects at least stage T4a disease
Additional specific MRI imaging staging subsets of rectal tumor

Special consideration should be given to low rectal tumors as these carry a different prognosis from higher lesions. This is predominantly due to anatomical considerations including waist-like tapering of the mesorectum 10

Early rectal cancer and significant polyps may also be subclassified, necessitating the use of good quality, high resolution T2-weighted MR images. This relies on the recognition that most rectal tumors (apart from mucinous tumors) have intermediate T2 signal compared to hyperintense submucosa and hypointense muscularis layers 9. Such staging may be helpful in selecting less extensive surgical resection options.

  • Low rectal tumor staging 10
    • Stage 1: Tumor confined to bowel wall with intact outer muscularis propria
    • Stage 2: Tumor replaces muscularis propria but does not extend into intersphincteric plane
    • Stage 3: Tumor invades intersphincteric plane or lies within 1mm of levator muscles
    • Stage 4: Tumor invades external anal sphincter and is within 1mm and beyond levators with or without invading adjacent organs
  • Early rectal tumor staging 9
    • T0/early T1sm1: no submucosa (sm) disruption evident with entire thickness of submucosal stripe preserved
    • T1sm2: at least 1mm of submucosa preserved
    • T1sm3/early T2: less than 1mm of submucosa preserved but full thickness of muscularis propria preserved
    • T2 early: more than 1mm muscularis propria preserved
    • T2/T3a: 0mm muscularis propria preserved / less than 1mm microscopic invasion beyond muscularis propria (prognosis identical)
    • T3b: 1-5mm invasion beyond muscularis propria (still carries good prognosis)

See also

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