Stages
The wall of the colon and rectum is made up of layers of tissues. Colorectal cancer starts in the inner layer and can grow through some or all of the other layers. It can also spread to other parts of the body.
Once colorectal cancer is detected, additional tests such as X-rays, CT, MRI and PET scans are performed to determine how far the cancer has progressed. This process is called staging. The stage of the disease greatly influences both treatment and survivability.
According to the American Cancer Society, the most commonly used staging system for colorectal cancer is that of the American Joint Committee on Cancer (AJCC) also known as the TNM system. This system describes:
- The Tumor - how far it has grown and whether or not it has grown into nearby areas
- Lymph Node involvement
- Metastasis - the spread of the cancer to other parts of the body
Numbers following each of these letters indicate their severity. This information is used to determine which stage the cancer is in. The stage is identified by the Roman numerals I through IV. These numbers may be further subdivided using letters A, B and C. In general, stages mean the following:
Stage 0: The cancer is contained to only the innermost lining of the colon or rectum.
Stage I: The tumor has grown into but not through the inner wall of the colon or rectum.
Stage II: The tumor extends farther into, or may have passed through the wall of the colon or rectum and may have invaded nearby tissue, but there is no involvement of the lymph nodes.
Stage III: The cancer has spread to nearby lymph nodes, but not to other parts of the body.
Stage IV: The cancer has spread to other parts of the body, such as the liver or lungs.
Recurrent: After a period of absence, the cancer has returned to the colon, rectum or another part of the body.
