Staging of Colorectal Cancer
Colon Cancer Staging

It is important to determine the stage, or extent, of your tumor to help establish the treatment plan that is best for you. How is this done?
 
The tests discussed in the previous section are used to help determine:
  • how deeply the tumor has invaded the lining of the colon or rectum;
  • if there are enlarged lymph nodes;
  • and whether the cancer has spread to adjacent organs or to other sites such as the liver or chest.
The lining of the colon and rectum is made up of concentric layers of tissue that resemble the rings of a tree. The innermost ring or layer of tissue is called the mucosa. The mucosa lines the colon and rectum. All colorectal cancers originate from this layer. Under the mucosa is a layer called the submucosa, and finally there is an outer muscle layer. As tumors grow, they invade the mucosa, and grow deeper into the submucosa and eventually into and through the muscle layer of the colon. Once the muscular wall of the colon has been compromised, tumors can extend into organs that are adjacent to the colon or rectum. Tumors can also spread into adjacent lymph nodes, or by invading into blood vessels that carry tumor cells to distant organs, most commonly the liver.
 
There are several formal systems used to stage colorectal cancers that are beyond the scope of this pamphlet. In general, colorectal cancer can be divided into early or advanced stages for the purposes of determining treatment plans.
 
Early stage: 
  • Tumors are limited to the superficial layers of the colon or rectum (mucosa or submucosa).
  • There is no spread to adjacent lymph nodes or organs.
  • There is no evidence of spread to distant organs, such as the liver.

 Surgery alone is typically performed without the need for additional treatment.

 Advanced stage if any of these factors are present:

  • The tumor has spread into the deeper muscle layers or through the wall of the colon or rectum.
  • Nearby lymph nodes or organs are affected by the tumor.
  • The tumor has spread to distant organs.
Surgery is still typically performed, but usually in combination with other forms of treatment such as chemotherapy for colon cancer, or chemotherapy and radiation therapy for rectal cancer.
 
Doctors use the American Joint Commission on Cancer (AJCC) system. The AJCC system is also called the TNM system, for Tumor extent, Nodal amount and presence of Metastases.  The levels of staging are described in the table below.

AJCC/TNM Staging

Tumor

Stage 0

Tis (carcinoma in-situ)

Superficially involves the mucosa.

Has not grown beyond the mucosa

Stage I

T1N0
T2N0

Invades through mucosa
Invades through submucosa

Stage II

T3N0
T4N0

Invades through muscle layers
Invades nearby tissues or organs

Stage III

Any T, N1-N3

Lymph nodes involved

Stage IV

Any T, Any N, M1

Distant Spread

 
Rectal Cancer Staging 
 

Rectal cancer staging is similar to colon cancer, with the addition of a special test called trans-rectal ultrasound.  This painless examination allows the depth of the tumor invasion and the status of the lymph nodes to be determined prior to surgery.  This information can guide treatment decisions regarding the type of surgery needed or the need for chemotherapy and radiation prior to an operation.

Early stage rectal cancers are primarily treated with surgery alone.  This includes Stage I or II tumors that are confined to the mucosa or submucosa and have not penetrated through the muscle layers.  The type of surgery that is recommended will depend on tumor size and tumor location.