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Colorectal Cancer Staging

What Staging Means

As colorectal cancer grows, it can spread through the wall of the colon or rectum. Then, like all cancers, it can spread (metastasize) to other parts of the body. The stage of your cancer is a way doctors describe how deep and how far your cancer has spread. Knowing the stage is important. The stage is a primary factor in deciding what treatment to use.

Systems for Staging

How colon cancer metastasizes
Click to enlarge: How
carcinoma in situ spreads
to become a metastatic
tumor.

Doctors need to know the stage of your cancer to know what treatment to recommend. There are three different systems doctors use for staging colorectal cancer. They are Dukes, Astler-Coller, and AJCC, which stands for American Joint Committee on Cancer. The AJCC, which is the most commonly used system for staging, is also called the TNM System. It is the system we describe here. Because staging is so important for deciding what treatment to use, you should ask your doctor to explain the stage of your cancer to you in terms you can understand.

The TNM system consists of several different components. Each one is given a score. Then the scores are grouped to determine an overall stage for your cancer. With the TNM system, there are two different types of stages. The first is the clinical stage. Your oncologist will determine this from a physical exam and from imaging tests such as a CT scan. The clinical stage is used to decide what type of surgery you need. Later, the tissue that is removed during surgery will be examined, and the cancer will be given a new stage called its pathologic stage. This stage will be used to decide what other treatment you might need, if any.

The stage of your cancer is based on the size and extent of your tumor, the number of lymph nodes that are involved, and whether the cancer has spread to distant organs.

The TNM System for Colon Cancer

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

Numerical values are assigned to the T, N, and M categories. There are also two other values that can be assigned. The first is X, which means the doctor does not have enough information to assess the tumor size, lymph node involvement, or metastatic spread. This value is often assigned before surgery. The other value is "in situ (is)." This 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 a value assigned by a Roman numeral I through IV (1 through 4). The higher the value, the more advanced your cancer is.
These are the stage groupings of colorectal cancer and what they mean.


What is Colorectal Cancer | Symptoms | Diagnosis | Staging | Risk Factors | Prevention

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