Colon Cancer Staging Tests

MRI being performed on patient
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Colon cancer staging is the process health professionals use to determine where the cancer went when no one was looking. Did it stay in the colon or work its way into the lymph nodes or other parts of the body?

Determining the colon cancer stage is an important part of choosing an appropriate treatment. If you've been diagnosed with colon cancer, there are many tools your doctor can use to determine the stage.

CT Scan - CAT Scan

CT stands for computed tomography. A CT scan (pronounced "cat scan") is a specialized type of x-ray that shows the doctor what a slice of you looks like. This is possible because the CT scan rotates around you while taking the x-ray. CT scans are great for providing detailed pictures of bones. You may have a dye injected, swallowed, or given as an enema so your organs will show up better on the CT scan. It is also sometimes performed as a virtual colonoscopy when multiple CT images are combined to show your colon in detail. The scan is done lying down and if you are anxious about it, you may be given a sedative before the scan.
More: What is a CT Scan?

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) also shows the doctor what a slice of you looks like, but it uses radio waves and magnets to do it. MRIs are great at taking pictures of soft tissue, like the colon.

You may have gadolinium injected prior to the MRI. It collects around cancer cells so they show up better in the scan. The MRI may be done in a closed system, which many find claustrophobic. An open MRI may be available. You need to be able to lie still, and the machine makes loud thumping noises during the scan.

More: What is an MRI?

PET Scan

The PET (positron emission tomography) scanner is yet another type of scan where the instrument rotates around your body. But in this case it is looking at the functions that set active cancer cells apart from regular cells. It uses a small amount of radioactive sugar, which cancer cells take up faster than normal cells. You may have to fast before this scan and reduce exercise in the day before the scan. You will receive an injection into a vein. The malignant cells will show up brighter than regular cells in this scan, showing where you may have tumors in the colon and where they may have spread.
More: What is a PET Scan?

Lymph Node Biopsy

Lymph nodes are like little filters located throughout the body, places where the immune system cells fight infection. Cancer cells can be found here if they are traveling outside of tumors and attempting to spread. Checking the lymph nodes for cancer cells gives your doctor an idea of how successful the cancer has been in digging out of your colon and traveling to other parts of your body.

Tumor Biopsy

During colonoscopy or surgery, tissues will be removed and sent to the lab to determine if they are cancerous and what type of cancer they are. This can tell your doctor whether they are the same kind of tumor and whether cancer has spread from one area of the body to another. They may be further analyzed by molecular marker tests.

CEA Assay

Your doctor may order a CEA Assay blood test. (Assay is just a fancy word for analysis.) This test is useful because certain levels of carcinoembryonic antigen (CEA) in the blood can be a sign that colon cancer is present and may have spread outside of the colon. It is not a specific test, as other medical conditions can cause results to be high.

The results of these, plus your physical exam will help your provider determine what stage to use to describe your case.

More: What Do Colon Cancer Stages Mean?


Colon Cancer (PDQ): Treatment: Stages of Colon Cancer. National Cancer Institute. Accessed 5 Dec 2015 [].

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