Revision 36 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. In rectal cancer, pre-treatment MRI is the evaluation of choice, guiding surgical and non-surgical management options. 

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) 7th ed, does not sub-classify T3. This is a feature of MRI staging but 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)

The size cut off for mesorectal nodes is usually taken at 5mm 6 

More recent analysis of data puts into question the importance of lymph nodes as a predictors of local recurrence and also questions the rational of size criteria for node assessment 9

  • Nx: regional nodes not assessed
  • N0: no regional lymph nodes
  • N1: metastasis in 1-3 regional (peri-rectal) lymph nodes
    • N1a: metastasis in one 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
  • 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, No, Mo
  • 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-contigous 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 (continous or discontinous) is within 1mm of the mesorectal fascia
    • peritoneal reflection does not constitute CRM, which if involved reflects at least stage T4a disease

See also

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