What Are the Stages of Colorectal Cancer?
Once colorectal cancer has been diagnosed, it’s important to know the stage of the cancer. The stage indicates how serious it is. The stage of colorectal cancer depends on the size of the cancer, lymph node involvement, and if there is any distant spread of the tumor. Knowing the stage helps the doctor plan the right course of treatment. A pathologist determines the stage by looking at the cells that are collected during the diagnosis process.
TNM is used for colorectal cancer staging and for all types of cancer. The letters TNM describe the amount and spread of cancer in the body. For colorectal cancer,
- T: indicates how far the tumor penetrates into the bowel wall.
- N: indicates whether the cancer has spread to surrounding lymph nodes.
- M: indicates metastasis, which means that cancer has spread to other parts of the body.
Using TNM, the doctor will assign a stage:
This is an extremely early stage. Abnormal cells are found only in the superficial layer of the colon wall. Stage 0 is also called carcinoma insitu.
This is a very early stage. Cancerous cells have been found in the muscular layer of the colon wall. However, it has not spread beyond the colon wall.
Cancer has spread through the muscle layer of the colon wall to the outermost layer of the colon wall. However, the cancer has not spread to the lymph nodes.
In Stage 3, colorectal cancer has spread to nearby lymph nodes but not to other parts of the body.
Cancer has spread beyond the colon to other parts of the body— most often the liver and lungs. This is an advanced stage.
There are many different tests to determine the stages of colorectal cancer, including:
- Urine and blood tests
- Additional physical exam
- X-rays of various parts of the body, including lungs, bladder, kidneys, lymph nodes
- Barium enema to check the colon and rectum
- CT scan —This series of x-rays put together by a computer provides detailed pictures of areas inside the body.
- Ultrasonography—In this procedure, sound waves are bounced off body tissues. The echoes create a picture.
- MRI scan —A magnet linked to a computer produces detailed pictures of areas inside the body.
- PET scan —This procedure looks for small amounts of cancer that may have spread or not responded to treatments. A radioactive sugar molecule is injected into a vein. It has a radioactive tracer on it. A scan is taken a few hours later. Because tumors use sugar faster than normal tissues, the tracer helps identify the tumor cells.
How Colorectal Cancer Spreads
There are three main ways that cancer spreads in the body. It can spread through:
- Tissue. Cancer invades nearby normal tissue.
- Lymph system. Cancer invades the lymph system and travels through the lymph vessels to other parts of the body.
- Blood. Cancer invades veins and capillaries and travels through the bloodstream to other parts of the body.
The original tumor is called the primary tumor. When cancer cells break away from it and travel to other places in the body, a secondary tumor can form. The name for this spreading process is metastasis.
The secondary tumor is the same kind of cancer as the primary tumor. For instance, if the cancer cells in the colon travel to the liver, it is called metastatic colon cancer. It is not liver cancer.
The liver is one of the most common places for colorectal cancer to spread. When colon or rectal cancer spreads to the liver, it is very serious. However, it can be treated and even cured.