Staging of Colorectal Cancer

If you are unfortunate enough to be diagnosed with colorectal cancer, this usually starts with a colonoscopy so as to discover the tumor. The size of the cancer does not bear much relevance. What truly matters is what is called the staging. The American Joint Committee on Cancer (AJCC) has accepted the TNM staging system based upon the tumor, lymph node status, and presence of metastatic disease. It can be summarized as follows:

  • Stage I: Cancer has grown only partially through the colon wall, but does not involve the surrounding lymph nodes. (T1-2, N0, M0)
  • Stage II: Cancer has grown through the colon wall, but does not involve the surrounding lymph nodes. (T3-4, N0, M0)
  • Stage III: Cancer has spread to the surrounding lymph nodes regardless of the depth of penetration of the tumor itself. Any T, N1 or 2, M0)
  • Stage IV: Cancer has spread into another organ or distant from the primary tumor regardless of the T or N stage. (Any T, Any N, M1)

With colon and rectal cancer the exact tumor stage may not be known until after surgery to remove the tumor and the surrounding lymphatics. This allows a pathologist to examine the specimen to determine the exact stage after microscopic evaluation of the main tumor and the many lymph nodes around the area. In most cases, however, pre-operative evaluation would include CT scan of the abdomen and pelvis (for colon and rectal cancers) and CT of the chest (for rectal cancers only due to their propensity for pulmonary metastases). The most common organs involved with metastatic disease are the liver and lungs. A blood test called a CEA (carcinoembryonic antigen) is also done as it can be helpful for baseline comparison to future results to watch for recurrent disease. So after the colon cancer has been found by colonoscopy, the CT scans and CEA are done, as long as metastatic disease is not found, one then proceeds to surgery to remove the section of colon containing the cancer.

For rectal cancers only (cancers of the distal 12-15 cm of the colon) usually an evaluation called endorectal ultrasound is also done. This involves placing a cylindrical ultrasound wand into the anus to evaluate the local stage of the tumor. This often guides the subsequent treatment as to whether to proceed to surgery for Stage I tumors or to pre-operative (aka Neoadjuvant) chemotherapy and radiation to downstage the tumor (Stages II and III) and make subsequent surgery more likely to be successful.

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