Colorectal Cancer: Stages

What does stage of cancer mean?

The stage of a cancer is how much and how far the cancer has spread in your body. Your healthcare provider uses exams and tests to find out the size of the cancer and where it is. He or she can also see if the cancer has grown into nearby areas, and if it has 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.

What are the stages of colorectal 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, like all cancers, it can spread, or metastasize, to other parts of the body. 

The TNM system for colorectal cancer

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 terms 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 the main tumor has spread into the lining of your colon or rectum and nearby tissue.

  • N tells whether or not the lymph nodes in the area of the original tumor have become cancer.

  • M tells whether or not the cancer has spread to other distant organs in the body, such as the liver, lung, or lining of your belly or abdomen.

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 tumor size, lymph node involvement, or spread of the cancer. This value is often assigned before surgery.

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

Stage groupings

Stage groupings are determined by combining the T, N, and M values from the TNM system. These groupings give an overall description of how advanced your cancer is. A stage grouping can have a value of 0 or of Roman numerals I through 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 of your colon or rectum. It has not spread and is in its earliest stage. This stage is also called carcinoma in situ.

Stage I. The cancer has spread to the middle layers of the lining of your colon or rectum. It has not spread to the 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 has not gone through them. It still has not spread to the lymph nodes or to distant sites.

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

  • Stage IIC. The cancer has grown outside your colon to nearby tissues or organs. But it has still not spread to the lymph nodes or to distant sites.

Stage III. This stage is divided into 3 groups:

  • Stage IIIA. One of the following applies:

  • The cancer has spread to the first or middle layers of your colon or rectum wall. It has also spread to 1 to 3 lymph nodes. 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. One of the following applies:

  • The cancer has grown into or through the outer layers of the colon or rectum. But it hasn't spread to nearby organs. It has spread to 1 to 3 nearby lymph nodes. 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 the first or 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. One of the following applies:

  • The cancer has grown through the outer layers of the colon or rectum but hasn't reached nearby organs. It has spread to 4 to 6 nearby lymph nodes. But it hasn’t spread to distant sites.

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

Stage IV. This stage is divided into 2 sub-stages:

  • 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, such as the lungs or liver. Or it has spread to 1 distant set of lymph nodes.

  • 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, such as the liver or the lungs. Or it has spread to a set of distant lymph nodes. Or it has spread to distant parts of the lining of the abdomen.

Talking with your healthcare provider

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.