Following a cancer diagnosis, your cancer team will work on staging it – that is, determining the extent of the disease; if the cancer has stayed within the colon or rectum, or has spread to other parts of the body. Staging will help determine the course of treatment.
Your cancer care team has many testing options, including X-rays, magnetic resonance imaging (MRI), computerized tomography (CT) scans, positron emission tomography (PET) scans, bone scans, blood tests, surgery and lymph node biopsies.
While some stages are broken down into multiple parts, the following is a basic guide to staging used for colorectal cancer:
- Stage 0 (carcinoma in situ): Abnormal cells are found in the innermost layer of the colon wall and, if left untreated, will become an invasive cancer.
- Stage I: Cancer has formed in the innermost layer of the colon wall and has spread to the next layer of tissue. It may have also spread to the muscle layer of the colon wall.
- Stage II: Cancer has spread through the muscle layer of the colon wall, through the outermost layer of the colon wall, or through the outermost layer of the colon wall and to nearby organs.
- Stage III: Cancer has spread through layers of the colon wall and to lymph nodes, or cancer cells are found in tissue surrounding the lymph nodes. Cancer may be present in nearby organs.
- Stage IV: Cancer has spread to a distant organ (or multiple organs) or lymph nodes. Cancer may have spread into the lining of the abdominal wall.