Colorectal Cancer: Stages

The stage of a cancer usually depends on its size and how far the cancer has spread in your body. Your healthcare provider uses a tissue sample of the tumor (biopsy), blood and other exams and imaging scans to stage colorectal cancer. A biopsy of the colorectal cancer is needed to report how deeply the cancer has grown through the layers of the colon. Imaging can show if the cancer has grown into nearby organs. Or spread to other parts of your body. The stage of a cancer is one of the most important things to know when deciding how to treat the cancer.

Colorectal cancer starts in the inner lining of the colon or rectum. As colorectal cancer grows, it can grow through the layers of the wall of the colon or rectum. Then it can spread (metastasize) to other parts of the body. 

The most commonly used system to stage colorectal cancer is the TNM system from the American Joint Committee on Cancer. Staging is very important for deciding what treatment to use. Be sure to ask your healthcare provider to explain the stage of your cancer to you in a way you can understand.

The first step in staging your cancer is to decide the value for each part of the TNM system. Here's what the letters stand for in the TNM system:

• T tells how far down the primary tumor has grown into the layers of your colon or rectum and nearby tissue.

• N tells if the lymph nodes near the original tumor have cancer cells in them.

• M tells if the cancer has spread (metastasized) to distant organs in the body, like the liver, lungs, or the lining of your abdomen (belly) called the peritoneum.

Number values are assigned to the T, N, and M categories. There are also 2 other values that can be assigned:

• X means the provider does not have enough information to assess the extent of the main tumor (TX), or if the lymph nodes have cancer cells (NX). This value is often assigned before surgery.

• In situ (is) means the cancer is in its earliest stages and has not spread beyond the first layer of the colon or rectum wall (Tis).

Stage groupings are done by combining the T, N, and M values from the TNM system. These groupings give an overall description of how advanced the cancer is. A stage grouping can have a value of 0 or 1 through 4 (using Roman numerals I, II, III, and IV). The higher the number, the more advanced your cancer is.

These are the stage groupings of colorectal cancer and what they mean:

Stage 0. Cancer is only in the innermost lining layer of the colon or rectum (called the mucosa). This stage is also called carcinoma in situ.

Stage I. The cancer has spread deeper than the lining, into the middle layers of the colon or rectum wall. It has not spread to lymph nodes or distant sites.

Stage II. This stage is divided into 3 groups:

• Stage IIA. The cancer has grown into the outermost layers of the colon or rectum, but it has not gone through them. It has not spread to lymph nodes or distant sites.

• Stage IIB. The cancer has grown through the outer lining of the colon or rectum, but it has not grown into nearby tissues or organs. It has not spread to lymph nodes or distant sites.

• Stage IIC. The cancer has grown outside the colon or rectum to nearby tissues or organs. It has not spread to lymph nodes or distant sites.

Stage III. This stage is divided into 3 groups:

• Stage IIIA. Is 1 of the following:

  • The cancer has spread to the first or middle layers of your colon or rectum wall. It has also spread to 1 to 3 nearby lymph nodes or the fat around them. It hasn't spread to distant sites.
  • The cancer has grown into the first layer of the colon or rectum wall. It has also spread to 4 to 6 nearby lymph nodes. It hasn't spread to distant sites.

• Stage IIIB. Is 1 of the following:

  • The cancer has grown into or through the outer layers of the colon or rectum. It hasn't spread to nearby organs. It has spread to 1 to 3 nearby lymph nodes or the fat around them. It has not spread to distant sites.
  • The cancer has grown into the middle or outer layers of the colon or rectum. It has spread to 4 to 6 nearby lymph nodes. It hasn't spread to distant sites.
  • The cancer has grown into at least the first and middle layers of the colon or rectum. It has spread to 7 or more nearby lymph nodes. It hasn't spread to distant sites.

• Stage IIIC. Is 1 of the following:

  • The cancer has grown through the outer layers of the colon or rectum, but it hasn't reached nearby organs. It has spread to 4 to 6 nearby lymph nodes. It hasn’t spread to distant sites.
  • The cancer has grown into or through the outer layers of the colon or rectum, but it hasn't reached nearby organs. It has spread to 7 or more nearby lymph nodes. It hasn’t spread to distant sites.
  • The cancer has grown through the outer layers of the colon or rectum and has reached nearby organs. It has spread to 1 or more nearby lymph nodes or into fat near the lymph nodes. It hasn’t spread to distant sites.

Stage IV. This stage is divided into 2 substages:

• Stage IVA. The cancer may or may not have grown through the wall of the colon or rectum. It may or may not have reached nearby lymph nodes. It has spread to 1 distant organ, like the lungs or liver. Or it has spread to 1 distant set of lymph nodes. It has not spread to distant parts of the lining of the abdomen (the peritoneum).

• Stage IVB. The cancer may or may not have grown through the wall of the colon or rectum. It may or may not have reached nearby lymph nodes. It has spread to more than 1 distant organ, like the liver or the lungs. Or it has spread to a set of distant lymph nodes. It has not spread to distant parts of the peritoneum.

• Stage IVC. The cancer may or may not have grown through the wall of the colon or rectum. It may or may not have reached nearby lymph nodes. It has spread to distant parts of the peritoneum and may or may not have spread to distant organs or lymph nodes.

Once your cancer is staged, your healthcare provider will talk with you about what the stage means for your treatment. Make sure to ask any questions or talk about your concerns.