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CRC: STAGING
Slides last updated: March 2015
How colorectal cancer (CRC) is staged1
Stage describes the extent of cancer, and is one of the most important
factors in determining prognosis and treatment options
For CRC, stage is based on how far the cancer has grown into the
intestinal wall, if it has reached nearby structures, and if it has spread to
distant organs
Staging is the process of determining how far the cancer has spread, and
involves physical exam, biopsies, imaging tests and results of surgery
Clinical staging uses results of the physical exam, biopsy and imaging
tests. Pathologic staging combines these tests with results from surgery
1. American Cancer Society. Colorectal Cancer Detailed Guide, 2014. Available online from
http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf, last accessed on 17/03/2015.
TNM classification is the most commonly used system1
Growth
Primary tumour (T)
Spread
Regional lymph nodes (N)
Metastasis
Distant metastasis (M)
1. American Cancer Society. Colorectal Cancer Detailed Guide, 2014. Available online from
http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf, last accessed on 17/03/2015.
The TNM staging system for CRC: T1
T categories describe the extent of spread through the layers that
form the wall of the colon and rectum
These layers, from inner to outer, include:
•Mucosa – inner lining
•Muscularis mucosa – a thin muscle layer
•Submucosa – the fibrous tissue beneath this muscle layer
•Muscularis propria – a thick muscle layer that contracts to force the
contents of the intestines along
•Subserosa and serosa – the thin outermost layers of connective
tissue that cover most of the colon
1. American Cancer Society. Colorectal Cancer Detailed Guide, 2014. Available online from
http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf, last accessed on 17/03/2015.
The TNM staging system for CRC: T1
Tx: No description is possible due to incomplete information
Tis: The cancer is at its earliest stage (in situ) and involves only the
mucosa; it has not grown beyond the muscularis mucosa
T1: The cancer has grown through the muscularis mucosa and extends
into the submucosa
T2: The cancer has grown through the submucosa and extends into the
muscularis propria
T3: The cancer has grown through the muscularis propria and into the
outermost layers of the colon or rectum, but not through them
T4a: The cancer has grown through the serosa, the outermost lining
T4b: The cancer has grown through the wall of the colon or rectum and is
attached to or has invaded nearby tissue or organs
1. American Cancer Society. Colorectal Cancer Detailed Guide, 2014. Available online from
http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf, last accessed on 17/03/2015.
The TNM staging system for CRC: N1
N categories indicate whether the cancer has spread to nearby lymph
nodes, and if so, how many lymph nodes may be involved
For an accurate estimation of lymph node involvement, ≥12 lymph nodes
are removed during surgery and examined under a microscope
Nx: No description is possible
N0: No cancer cells in nearby lymph nodes
N1: Cancer cells found in 1-3 nearby lymph nodes
•N1a: 1 lymph node
•N1b: 2-3 lymph nodes
•N1c: Small deposits of cells found in areas of fat near lymph nodes,
but not in the nodes themselves
N2: Cancer cells found in ≥4 nearby lymph nodes
•N2a: 4-6 lymph nodes
•N2b: ≥7 lymph nodes
1. American Cancer Society. Colorectal Cancer Detailed Guide, 2014. Available online from
http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf, last accessed on 17/03/2015.
The TNM staging system for CRC: M1
M categories indicate whether the cancer has spread (metastasised) to
distant organs such as the liver, lungs or distant lymph nodes
M0: No distant spread is seen
M1a: Cancer has spread to one distant organ or set of lymph nodes
M1b: Cancer has spread to more than one distant organ or set of lymph
nodes, or to distant parts of the peritoneum (lining of the abdominal
cavity)
Once the T, N and M categories have been determined – usually after
surgery – the information is combined in a process called stage grouping
Stages range from stage I (least advanced) to stage IV (most advanced)
1. American Cancer Society. Colorectal Cancer Detailed Guide, 2014. Available online from
http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf, last accessed on 17/03/2015.
Stages in CRC1
Cancer progression
Stage 0
Stage I
Stage IIA
Stage IIIA
Stage IVA
Tis, N0, M0
T1-T2, N0, M0
T3, N0, M0
T1-T2, N1, M0
T1, N2a, M0
Any T, any N,
M1a
Stage IIIB
Stage IVA
T3-T4a, N0, M0
T2-T3, N2a, M0
T1-T2, N2b, M0
Any T, any N,
M1b
Stage IIB
T4a, N0, M0
Stage IIC
T4b, N0, M0
Stage IIIC
T4b, N0, M0
T3-T4a, N2b, M0
T4b, N1-N2, M0
1. American Cancer Society. Colorectal Cancer Detailed Guide, 2014. Available online from
http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf, last accessed on 17/03/2015.
Survival rates for CRC by stage1
Five-year relative survival rate
100
Colon cancer
Survival rate (% )
80
Rectal cancer
Refers to the
percentage of
patients who live at
least 5 years after
diagnosis
60
40
20
0
I
IIA
IIB
IIIA
IIIB
IIIC
IV
Relative survival
rates compare
observed survival
with what would be
expected without
cancer
Stage
1. American Cancer Society. Colorectal Cancer Detailed Guide, 2014. Available online from
http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf, last accessed on 17/03/2015.
Grades of CRC1
Survival is also affected by the grade of cancer
Grade describes how closely the cancer looks like normal tissue when
viewed under a microscope
•Grade 1 (G1): cancer looks much like normal colorectal tissue
•Grade 4 (G4): cancer looks very abnormal
•Grades 2 and 3 (G2 and G3) fall in between G1 and G4
Often simplified to either low grade (G1, G2) or high grade (G3, G4)
Low-grade cancers tend to grow and spread more slowly than highgrade cancers
The outlook for low-grade cancers tends to be better than for high-grade
cancers
1. American Cancer Society. Colorectal Cancer Detailed Guide, 2014. Available online from
http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf, last accessed on 17/03/2015.