Understanding Colorectal Cancer: Stages

What “Stages” Mean

Once colorectal cancer has been diagnosed, it’s important to know the stage of the cancer. The stage indicates how serious it is. The stage of colorectal cancer depends on the size of the cancer, lymph node involvement, and if there is any distant spread of the tumor. Knowing the stage helps the doctor plan the right course of treatment. A pathologist determines the stage by looking at the cells that are collected during the diagnosis process.

The TNM staging system is used for all types of cancer, not just colorectal cancer. The letters TNM describe the amount and spread of cancer in the body. For colorectal cancer,

  • T: indicates how far the tumor penetrates into the bowel wall.
  • N: indicates whether the cancer has spread to surrounding lymph nodes.
  • M: indicates metastasis, which means that cancer has spread to other body parts.

Using TNM, the doctor will assign a stage:

Stage 0

This is an extremely early stage. Abnormal cells are found only in the superficial layer of the colon wall. Stage 0 is also called carcinoma in situ.

Stage 1

This is a very early stage. Cancerous cells have been found in the muscular layer of the colon wall. However, it has not spread beyond the colon wall.

Stage 2

Cancer has spread through the muscle layer of the colon wall to the outermost layer of the colon wall. However, the cancer has not spread to the lymph nodes.

Stage 3

In Stage 3, cancer has spread to nearby lymph nodes but not to other parts of the body.

Stage 4

Cancer has spread beyond the colon to other parts of the body—most often the liver and lungs. This is an advanced stage.

There are many different tests to determine the cancer’s stage, including:

  • Additional physical exam
  • X-rays of various parts of the body, including lungs, bladder, kidneys, lymph nodes
  • CT scan: a series of x-rays put together by a computer which provides detailed pictures of areas inside the body.
  • Rectal Endoscopic Ultrasound: a procedure used to stage rectal cancer. A special endoscope with ultrasound capabilities is inserted into the rectum and sound waves bounce off body tissues to create a picture. Tissue can be obtained using a needle. This is called a fine needle aspiration (FNA). You will be sedated for this procedure.
  • PET scan: procedure which looks for small amounts of cancer that may have spread or not responded to treatments. A radioactive sugar molecule is injected into a vein. It has a radioactive tracer on it. A scan is taken a few hours later. Because tumors use sugar faster than normal tissues, the tracer helps identify the tumor cells.
  • MRI scan (magnetic resonance imaging): MRIs are similar to CT scans. An MRI scan provides detailed pictures like CT scans. The difference is that MRI scans use radio waves and strong magnets instead of X-rays. The energy from the radio waves produces patterns. A computer takes these and turns them into detailed images of specific parts of your body.
  • Blood tests: Certain blood tests can point to advanced cancer. For example, liver function tests are often abnormal if the cancer has spread to your liver. Some cancers cause substances in the blood to rise. These substances are called tumor markers. CEA (carcinoembryonic antigen) is a tumor marker for colon cancer.
  • Biopsy: a small piece of tissue is taken from the liver or lymph node by a doctor either during a special CT procedure or surgery. The pathologist looks at the tissue under a microscope to see if there are any cancerous cells. 

Next: How does colorectal cancer spread? 

Back to “Understanding Colorectal Cancer: An Introduction”