Colorectal cancer stages

After a colorectal cancer diagnosis, doctors determine the stage of the disease before deciding how best to treat it. Most cancer types, including colorectal cancer, are grouped into stages ranging from 0 to 4.

Stages are based on the cancer’s size, location and spread within the body. To establish the stage of colorectal cancer, the care team typically considers all of the information gathered during tests, exams or procedures leading up to a diagnosis. In some cases, additional tests may be recommended.

Tests used in colorectal cancer staging

Some of the diagnostic tests that play a role in staging colorectal cancer include:

• Biopsy
• Magnetic resonance imaging (MRI)
• Computed tomography (CT) scan
• Ultrasound exam
• Chest X-ray 
• Lymph node biopsy
• Surgery
• Complete blood count
• Carcinoembryonic antigen (CEA) test

Stages of colorectal cancer

Colorectal cancer is staged using the American Joint Committee on Cancer’s TNM system. This system differentiates stages based on the following information listed below.

T (tumor): This refers to the size of the primary tumor. The measurement also evaluates to what extent, if any, the cancer has spread to tissues in the colon or rectum.

N (node): This describes the involvement of lymph nodes near the primary tumor. Lymph nodes are small, bean-shaped clusters of immune system cells that are crucial to fighting infections. They’re usually one of the first sites in the body where cancer spreads.

M (metastasis): This indicates whether the cancer has spread (metastasized) to other areas of the body.  

A number (0-4) or the letter X is assigned to each factor. Using this colorectal cancer staging system, a higher number indicates increasing severity. For instance, a T1 score indicates a smaller tumor than a T2 score. The letter X means the information couldn’t be assessed.

The earliest colorectal cancer stage is 0, followed by four main stages, 0-4.

Substages within some of the main stages (like stage 2A or 2B) help account for specific details, such as which layer of the colon or rectum wall the cancer has reached. Substages are marked by letters, with letters that come earlier in the alphabet indicating a lower substage.

Below are the characteristics of each colorectal cancer stage.

Stage 0 colorectal cancer

In this, the earliest stage of colorectal cancer (also called carcinoma in situ or intramucosal carcinoma), the cancer cells are contained to the rectum's or colon's inner lining. This stage is also marked by this characteristic: 

• Abnormal cells are found in the innermost layer (mucosa) that lines the colon or rectum, but these cells have not become cancerous.

Stage 1 colorectal cancer

In stage 1, colorectal cancer cells are found in deeper layers of the colon or rectum wall, but they haven't spread beyond the wall. This stage is also marked by these specific characteristics:

• Cancer cells are found in the innermost layer lining the colon or rectum, and they have grown into the second layer of tissue (the submucosa).
• The cancer may have also spread to a nearby muscle layer (muscularis propria) but hasn’t reached nearby lymph nodes.

Stage 2 colorectal cancer

Stage 2 colorectal cancers have not spread to the lymph nodes, but some may have spread through and beyond the wall of the colon or rectum, sometimes into nearby tissues or organs. They are also marked by these specific characteristics:.

• Stage 2A:
  • The cancer has spread through the layers of the colon or rectum wall and has reached the outermost layer, but no farther.
• Stage 2B:
  • The cancer has grown past the outermost layer of the colon or rectum wall but hasn’t spread to nearby tissues or organs.
• Stage 2C:
  • The cancer has spread past the outermost layer of the colon or rectum wall and has grown into nearby tissues or organs, but it hasn’t spread to lymph nodes or distant organs.

Stage 3 colorectal cancer

In stage 3, colorectal cancer cells have spread to one or more nearby lymph nodes, but they have not grown beyond the lymph nodes and colon or rectum wall to other parts of the body. They are also marked by these specific characteristics:

• Stage 3A:
  • The cancer has spread through the first two inner layers of the colon or rectum wall (mucosa and submucosa) and may have also reached the third layer (muscularis propria). It has also reached one to three nearby lymph nodes, or cancer cells are found near the lymph nodes.
  • Or the cancer has spread through the first two layers of the colon or rectum wall and has reached four to six nearby lymph nodes.
• Stage 3B:
  • The cancer has reached the outermost layer (serosa) of the colon or rectum wall. It may have spread through the tissue that lines the abdominal organs (visceral peritoneum) but has not yet reached nearby organs. Cancer is found in one to three nearby lymph nodes, or cancer cells are found near the lymph nodes.
  • Or the cancer has grown into the muscle layer or the outermost layer of the colon or rectum wall and has reached four to six nearby lymph nodes.
  • Or the cancer has grown through the first two layers of the colon or rectum wall and may have reached the muscle layer. Cancer is found in seven or more nearby lymph nodes.
• Stage 3C:
  • The cancer has grown past the colon or rectum wall and has spread to the tissue that lines the abdominal organs, but it has not spread to nearby organs. Cancer is found in four to six nearby lymph nodes.
  • Or the cancer has grown past the colon or rectum wall or has spread through the tissue that lines the abdominal organs. It’s found in seven or more nearby lymph nodes.
  • Or the cancer has spread past the wall of the colon or rectum and has grown into nearby organs or tissues. Cancer is found in at least one nearby lymph node, or cancer cells are found near the lymph nodes.

Stage 4 colorectal cancer

Stage 4 colorectal cancer, also called metastatic colorectal cancer, has spread beyond the colon or rectum to distant areas of the body, including tissues and/or organs. They are also marked by these specific characteristics:

• Stage 4A: The cancer has reached one area or organ that isn’t near the colon or rectum (such as the liver, lung, ovary or a faraway lymph node).
• Stage 4B: The cancer has reached more than one area or organ that isn’t near the colon or rectum.
• Stage 4C: The cancer has spread to distant parts of the tissue that lines the abdominal wall and may have reached other areas or organs.

Colorectal cancer survival rate

One way cancer patients can estimate life expectancy is to review the five-year relative survival rate for that cancer type. This statistic indicates how many people with the same type of cancer are alive five years or more after a diagnosis, compared to people who don’t have that cancer type. The overall five-year relative survival rate for colorectal cancer is 65 percent.

The National Cancer Institute SEER Program further bases the survival rate for colorectal cancers on how far the cancer has spread.

Localized: The cancer hasn’t spread outside the primary site. The five-year relative survival rate for localized colorectal cancer is 90.9 percent.

Regional: The cancer has spread from the area of origin to nearby lymph nodes or structures. The five-year survival rate for regional colorectal cancer is 73.4 percent.

Distant: The cancer has spread to structures that are farther away from the colorectal region, such as the lungs. The five-year survival rate for distant colorectal cancer is lower—about 15.6 percent.