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It’s important to understand that colorectal cancer is a collective term used to describe cancer that starts in the colon, rectum, or both. These cancers can also be named colon cancer or rectal cancer, depending on where they start: 

  • Colon cancer is a type of cancer that begins in the large intestine (colon). The colon is the final part of the digestive tract.
  • Rectal cancer is a cancer that begins in the rectum— the last several inches of the large intestine. The rectum starts at the end of the final segment of your colon and ends when it reaches the short, narrow passage leading to the anus.

If either of these cancers spread, or metastasize, to the lungs, liver, or any other organ, it is called metastatic colorectal cancer. In most cases, the liver is the first to be affected, however, cells may also spread to the lungs, bones, brain, or spinal cord. Keep in mind that metastatic colorectal cancer is different than recurrent colorectal cancer, which is cancer that returns to the same part of the colon or rectum after treatment, rather than spreading to a different area of the body. 

Determining the Extent of Colorectal Cancers

If you have been diagnosed with colon cancer, your doctor will recommend tests to determine if your cancer has spread, and if so, how far. This process is known as staging. Knowing the stage (extent) of your cancer will help your care team at Rocky Mountain Cancer Centers (RMCC): 

  • Understand how serious your cancer is and your chances of survival
  • Plan the best treatment for you
  • Identify clinical trials that may be treatment options for you

Some staging tests your doctor could recommend may include imaging procedures such as abdominal, pelvic, and chest CT scans. In many cases, the stage of your cancer may not be fully determined until after colon cancer surgery.

While there are many staging systems, the TNM system, created by the American Joint Committee on Cancer (AJCC), is the most widely used. 

TNM stands for: 

  • T: the size of the tumor and any spread of cancer into nearby tissue
  • N: the spread of cancer to nearby lymph nodes
  • M: metastasis (spread of cancer to other parts of the body)

In your pathology report, the stage of your cancer will be indicated by Roman numerals that range from 0 to IV. As a general rule, the lower the number, the less the cancer has spread. By stage IV, the cancer is considered advanced and has spread (metastasized) to other areas of the body.

Stages of Colorectal Cancer

Below is a more detailed breakdown of how your doctor will describe colorectal cancer by its stage:

  • Stage 0: This means the cancer is found only in the innermost lining of the colon or rectum. Carcinoma in situ is another name for Stage 0 colorectal cancer.
  • Stage I: In this stage, the tumor has grown into the inner wall of the colon or rectum. The tumor has not grown through the wall.
  • Stage II: Here, the tumor extends more deeply into or through the wall of the colon or rectum. It may have invaded nearby tissue, but cancer cells have not spread to the lymph nodes.
  • Stage III: This stage means the cancer has spread to nearby lymph nodes, but not to other parts of the body.
  • Stage IV: This highest stage means the cancer has spread to other parts of the body, such as the liver or lungs.
  • Recurrence: This is cancer that has been treated and has returned after a period of time when the cancer could not be detected. The disease may return in the colon or rectum, or in another part of the body.

We at RMCC understand that a colorectal cancer diagnosis can be overwhelming. Just know that we are here for you every step of the way, focused on providing you with the best treatment and overall cancer care. From start to finish, we believe in treating the whole person, not just the disease.

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