The stage describes the extent of the cancer in the body. It is based on how far the cancer has grown into the wall of the intestine, whether or not it has reached nearby structures, and whether or not it has spread to the lymph nodes or distant organs. The stage of a cancer is one of the most important factors in determining prognosis and treatment options.

Staging is the process of finding out how far a cancer has spread. It is based on the results of the physical exam, biopsies, imaging tests (CT or MRI scan, x-rays, PET scan, etc. which are described in the section "How is colorectal cancer diagnosed?"), and the results of surgery.

There are actually 2 types of staging for colorectal cancer. The clinical stage is your doctor's best estimate of the extent of your disease, based on the results of the physical exam, biopsy, and any imaging tests you have had. If you have surgery, your doctors can also determine the pathologic stage, which is based on the same factors as the clinical stage, plus what is found as a result of the surgery. Because most patients with colorectal cancer have surgery, the pathologic stage is most often used when describing the extent of this cancer. Pathologic staging is likely to be more accurate than clinical staging, as it allows your doctor to get a firsthand impression of the extent of your disease.

AJCC (TNM) Staging System

A staging system is a standardized way in which the cancer care team describes the extent of the cancer. The most commonly used staging system for colorectal cancer is that of the American Joint Committee on Cancer (AJCC), sometimes also known as the TNM system. Older staging systems for colorectal cancer, such as the Dukes and Astler-Coller system, are mentioned briefly below for comparison. The TNM system describes 3 key pieces of information:

• T describes how far the main (primary) tumor has grown into the wall of the intestine and whether it has grown into nearby areas.

• N describes the extent of spread to nearby (regional) lymph nodes. Lymph nodes are small bean-shaped collections of immune system cells that are important in fighting infections.

• M indicates whether the cancer has spread (metastasized) to other organs of the body. (Colorectal cancer can spread almost anywhere in the body, but the most common sites of spread are the liver and lungs.)

Numbers or letters appear after T, N, and M to provide more details about each of these factors. The numbers 0 through 4 indicate increasing severity. The letter X means "cannot be assessed because the information is not available."

T categories for colorectal cancer

T categories of colorectal cancer describe the extent of spread through the layers that form the wall of the colon and rectum. These layers, from the inner to the outer, include:

• the inner lining (mucosa)
• a thin muscle layer (muscularis mucosa)
• the fibrous tissue beneath this muscle layer (submucosa)
• a thick muscle layer (muscularis propria) that contracts to force the contents of the intestines along
• the thin, outermost layers of connective tissue (subserosa and serosa) that cover most of the colon but not the rectum

The layers of the colon wall

N categories for colorectal cancer

N categories indicate whether or not the cancer has spread to nearby lymph nodes and, if so, how many lymph nodes are involved. To get an accurate idea about lymph node involvement, most doctors recommend that at least 12 lymph nodes be removed during surgery and looked at under a microscope.

M categories for colorectal cancer

M categories indicate whether or not the cancer has spread (metastasized) to distant organs, such as the liver, lungs, or distant lymph nodes.

Stage grouping

Once a person's T, N, and M categories have been determined, usually after surgery, this information is combined in a process called stage grouping. The stage is expressed in Roman numerals from stage I (the least advanced) to stage IV (the most advanced). Some stages are subdivided with letters.

Stage 0

Tis, N0, M0: The cancer is in the earliest stage. It has not grown beyond the inner layer (mucosa) of the colon or rectum. This stage is also known as carcinoma in situ or intramucosal carcinoma.

Stage I

T1, N0, M0 or T2, N0, M0: The cancer has grown through the muscularis mucosa into the submucosa (T1) or it may also have grown into the muscularis propria (T2). It has not spread to nearby lymph nodes or distant sites.

Stage IIA

T3, N0, M0: The cancer has grown into the outermost layers of the colon or rectum but has not reached nearby organs. It has not yet spread to the nearby lymph nodes or distant sites.

Stage IIB

T4, N0, M0: The cancer has grown through the wall of the colon or rectum and into other nearby tissues or organs. It has not yet spread to the nearby lymph nodes or distant sites.

Stage IIIA

T1, N1, M0 or T2, N1, M0: The cancer has grown through the mucosa into the submucosa (T1) or it may also have grown into the muscularis propria (T2). It has spread to 1 to 3 nearby lymph nodes but not to distant sites.

Stage IIIB

T3, N1, M0 or T4, N1, M0: The cancer has grown into the outermost layers of the colon or rectum but has not reached nearby organs (T3) or the cancer has grown through the wall of the colon or rectum and into other nearby tissues or organs (T4). It has spread to 1 to 3 nearby lymph nodes but not distant sites.

Stage IIIC

Any T, N2, M0: The cancer may or may not have grown through the wall of the colon or rectum, but it has spread to 4 or more nearby lymph nodes. It has not spread to distant sites.

Stage IV

Any T, Any N, M1: The cancer may or may not have grown through the wall of the colon or rectum, and it may or may not have spread to nearby lymph nodes. It has spread to distant sites such as the liver, lung, peritoneum (the lining of the abdominal cavity), or ovary.

Comparison of AJCC, Dukes, and Astler-Coller stages

If your stage is reported in letters rather than numbers, your doctor is likely referring to one of the other staging systems sometimes used for colorectal cancer. This table can be used to find the matching AJCC/TNM stage. As you can see, the Dukes and Astler-Coller staging systems often combine different AJCC stage groupings and are not as precise.

If you have any questions about your stage, please ask your doctor to explain the extent of your disease.

Survival rates for colorectal cancer by stage

Survival rates are a way for doctors to discuss and compare the prognosis (outlook) for patients, based on the stage of the cancer or other traits. There are some important points to note about these numbers:

• The 5-year survival rate refers to the percentage of patients who live at least 5 years after being diagnosed. Many of these people live much longer than 5 years after diagnosis.

• While these numbers are among the most current we have available, they represent people who were first diagnosed and treated many years ago. Several improvements in treating colorectal cancer have been made since then, and the survival rates for people now being diagnosed with these cancers may be higher.

• Survival statistics can sometimes be useful as a general guide, but they may not accurately represent any one person's prognosis. A number of other factors, including other tumor characteristics and a person's age and general health, can also affect outlook. Your doctor is likely to be a good source as to whether these numbers may apply to you, as he or she is familiar with the aspects of your particular situation.

Survival rates for colon cancer by stage

The numbers below come from a study of the National Cancer Institute's SEER database, looking at nearly 120,000 people diagnosed with colon cancer between 1991 and 2000.

*In this study, survival was better for stage IIIA than for stage IIB. The reasons for this are not clear, and it is not known if this is still the case.

Relative survival rates for rectal cancer by stage

Accurate survival statistics for rectal cancer are a little harder to find, as it is a less common disease. The numbers below come from the National Cancer Institute's SEER database, looking at people diagnosed with rectal cancer between 1988 and 2001.

These numbers are relative survival rates. A standard 5-year survival rate refers to the percentage of patients who live at least 5 years after their cancer is diagnosed; it includes people with rectal cancer who may die of other causes, such as heart disease. Five-year relative survival rates reflect the chances of not dying specifically from rectal cancer. As with standard survival rates, these rates are based on patients diagnosed and treated more than 5 years ago. Improvements in treatment since then may result in a better outlook for recently diagnosed patients.

Grade of colorectal cancer

Another factor that can affect the outlook for survival is the grade of the cancer. Grade is a description of how closely the cancer resembles normal colorectal tissue when looked at under a microscope.

The scale used for grading colorectal cancers goes from G1 (where the cancer looks much like normal colorectal tissue) to G4 (where the cancer looks very abnormal). The grades G2 and G3 fall somewhere in between. The grade is often simplified as either "low-grade" (G1 or G2) or "high-grade" (G3 or G4).

Most of the time, the outlook is better for low-grade cancers than it is for high-grade cancers of the same stage. Doctors sometimes use this distinction to decide whether a patient should get additional (adjuvant) treatment with chemotherapy after surgery (discussed in more detail in the section, "Chemotherapy").

Last Medical Review: 05/18/2009
Last Revised: 05/18/2009