# Radiation Oncology/Rectum/Staging
### Current Staging

AJCC 7th edition (2009)
Primary Tumor:
* T1 - invades submucosa
* T2 - invades muscularis propria
* T3 - invades through muscularis propria into pericolorectal tissues
* T4
** T4a - penetrates to the surface of the visceral peritoneum
** T4b - directly invades or is adherent to other organs or structures
Layers: are the epithelium, basement membrane (defines intraepithelial), lamina propria (defines intramucosal) - contains capillaries and lymphatics (but little chance for mets), muscularis mucosae, submucosa (loose connective tissue), muscularis propria (circular and longitudinal layers), subserosa (single layer of cells).
Difference between rectum and colon is that most of the rectum lacks serosa. Thus for the rectum, a T3 is invasion into perirectal fat; for colon, T3 is invasion of subserosa. Also for the rectum, T4 is only invasion of other organs, whereas for the colon T4 can also be perforation through serosa.
Regional Lymph Nodes:
* N1 - 1 to 3 lymph nodes
** N1a - 1 lymph node
** N1b - 2-3 lymph nodes
** N1c - tumor deposits in the subserosa, mesentery, or nonperitonealized pericolic or perirectal tissues without regional nodal metastasis
* N2 - 4 or more
** N2a - 4-6 lymph nodes
** N2b - 7 or more lymph nodes
Distant Metastasis:
* M0 - none
* M1 - yes
** M1a - metastasis confined to one organ or site
** M1b - metastasis in more than one organ/site or the peritoneum
Stage Grouping:
* I - T1-2 N0 M0
* IIA - T3 N0 M0
* IIB - T4a N0 M0
* IIC - T4b N0 M0
* IIIA - T1-2 N1 M0, T1 N2a M0
* IIIB - T3-T4a N1 M0, T2-T3 N2a, T1-T2 N2b
* IIIC - T4a N2a, T3-T4a N2b, T4b N1-N2
* IVA - M1a
* IVB - M1b
Changes from 6th edition:
* T4 subdivided into T4a/b
* N1 subdivided into N1a/b/c, N2 into N2a/b
* Added satellite tumor deposits (N1c)
* Stage II subdivided into IIA/B/C
* Stage III: T4bN1 was reclassified from IIIB to IIIC; T1N2a reclassified from IIIC to IIIA; T1N2b, T2N2, and T3N2a reclassified from IIIC to IIIB.
* M1 subdivided into M1a/b. Stage IV subdivided into IVA and IVB.
Dukes stage (1932):
* A - Growth limited to wall of rectum - T1-2 N0 (Stage I)
* B - Extra rectal tissues. No lymph node involvement - T3-4 N0 (IIA - IIB)
* C - Regional lymph nodes - N+ (IIIA-C)
** modified 1935: C1 - regional lymph nodes, C2 - mesenteric nodes
** named for Cuthbert E. Dukes
    No PMID - "The classification of cancer of the rectum." Dukes CE. J Pathol Bacteriol. 1932;35:323.
    No PMID - "Lymphatic spread in cancer of the rectum." Gabriel WB, Dukes C, et al. Br J Surg. 1935;23:395.
Modified Astler-Coller (1954):
* A - Limited to mucosa - T1 N0
* B1 - Involves muscularis propria but not through it - T2 N0
* B2 - Through muscularis propria - T3 N0
* B3 - T4 N0
* C1 - T1-2 N+
* C2 - T3 N+
* C3 - T4 N+
* D - M1
** PMID 13159135 [Full text on PMC] — "The prognostic significance of direct extension of carcinoma of the colon and rectum." Astler VB and Coller FA. Ann Surg. 1954 Jun;139(6):846-52.

### Older staging editions

AJCC 6th Edition (2002)
* T1 - invades submucosa
* T2 - invades muscularis propria
* T3 - invades into subserosa or into non-peritonealized pericoloic or perirectal tissues
* T4 - invades other organs or structures or perforates visceral peritoneum
* N1 - 1 to 3 lymph nodes
* N2 - 4 or more
Stage grouping:
* I - T1-2 N0 M0
* IIA - T3 N0 M0
* IIB - T4 N0 M0
* IIIA - T1-2 N1 M0
* IIIB - T3-4 N1 M0
* IIIC - N2
* IV - M1
Changes in AJCC staging:
* 6th ed: divided into IIA and IIB and into IIIA, B, C