Colon Cancer Stages: What Do They Mean?

Staging cancers helps doctors understand how advanced a cancer is, come up with the best treatment plan, and predict the path of the disease, including the chance of recovery.

Colon cancer is no different. There are several ways to test for what stage the colon cancer is in and monitor it while you are in treatment.

A colon cancer diagnosis or a rectal cancer diagnosis typically involves a biopsy — studying suspicious tissue from the colon or rectum under a microscope. If doctors discover cancer they will run tests to see how advanced the disease is and whether it has spread to other areas of the body.

• Biopsy A doctor may request a biopsy when an initial screening shows signs of cancer. During a biopsy, a small piece of tissue is removed from the colon and sent to a lab for evaluation.

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   In some cases, part of the colon may need to be removed as opposed to a small sample. Depending on what the biopsy shows, a molecular test may be next to look for changes and mutations in specific genes and proteins.
  
• Complete Blood Count (CBC) A CBC test is typically used to determine if you are anemic, or lack red blood cells. Anemia is caused by chronic bleeding from the tumor. Iron deficiency anemia is one of the most common symptoms in colorectal cancer.

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• Carcinoembryonic Antigen (CEA) A CEA test measures the amount of carcinoembryonic antigens in the blood.

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   CEAs don’t necessarily mean you have cancer, but some types of cancer, including colorectal cancer, produce more CEA than would normally be in your body.
  
• Chest X-Ray Doctors may use this test to see if cancer cells have spread to the lungs, but a CT scan is more common.
  
• Computerized Tomography (CT or CAT) Scan In this test, cross-sectional images of the body created with X-rays are examined for signs that colorectal cancer has spread to other organs like the liver.
  
• Liver Enzymes Liver enzymes are used to check how well your liver is functioning. These tests can potentially show if colorectal cancer has spread to the liver.

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• Magnetic Resonance Imaging (MRI) Scan Radio waves and strong magnets produce detailed images that can help doctors see cancerous growths. An endorectal MRI scans the pelvis area specifically and is used to see if the cancer has spread from the rectum to other places in the body.
• Positron Emission Tomography (PET) Scan Doctors inject a small amount of a radioactive sugar substance into the blood, then look to see how much it is absorbed by cells in different areas of the body. Cancer cells tend to absorb more of these sugars than normal cells because they require more energy to fuel their rapid growth.
  
• Surgery At very early stages, surgery may be used to remove all or part of a tumor, either by removing a polyp in a colonoscopy or removing a larger piece through local excision, cutting out a small cancer and some of the healthy tissue around it.

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   These surgeries can also be used to see if the cancer cannot fully be removed by small surgeries or if it has spread through the colon.

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• Ultrasound This device can spot tumors by creating sound waves and transforming echoes into images on a screen. A technician may use an abdominal ultrasound to see if there are tumors on the organs in your abdomen, such as on your liver or gallbladder. An endorectal ultrasound is used to see whether a cancer has grown through the rectal wall and spread to nearby organs. Intraoperative ultrasound is usually used during primary surgeries, or initial removals of tumors, for colorectal cancer.

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   If a tumor is detected on the liver during the surgery, a biopsy sample is taken.

The TNM system is organized around the answers to a series of questions.

• Tumor (T) Has the tumor grown beyond the inside lining of the colon or rectum and into the wall? If so, how many layers deep is it?
• Node (N) Has the tumor spread to the lymph nodes? If so, where and how many?
• Metastasis (M) Has the cancer spread beyond the lymph nodes to other parts of the body? If so, where and how much?

Once doctors make all these assessments, they combine this information to stage the cancer.

Generally, the higher the number and letter, the more advanced the cancer.

Stage 0

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

Stage 1

The cancer has grown into the submucosa, and possibly into the thick muscle layer beneath it (muscularis propria). It has not spread to nearby lymph nodes or distant sites (T1 or T2, N0, M0).

Stage 2A

The cancer has grown into the colon wall or rectum but not through it. It has not reached nearby organs or lymph nodes or spread to distant sites (T3, N0, M0).

Stage 2B

The cancer has grown through the wall of the colon or rectum but not into nearby tissue or organs. It has not spread to nearby lymph nodes or distant sites (T4a, N0, M0).

Stage 2C

The cancer has grown through the wall of the colon or rectum and is attached to or has grown into other nearby tissues or organs. It has not spread to nearby lymph nodes or distant sites (T4b, N0, M0).

Stage 3A

The cancer has grown into the submucosa and possibly the muscularis propria; it has spread to 1 to 3 nearby lymph nodes or into areas of fat near the lymph nodes, but not to distant sites (T1 or T2, N1/N1c, M0).

— or —

The cancer has grown into the submucosa and spread to 4 to 6 nearby lymph nodes but not to distant sites (T1, N2a, M0).

Stage 3B

The cancer has grown into the wall of the colon or rectum or through the visceral peritoneum (the inner lining of the abdominal cavity) but has not reached nearby organs. It has spread to 1 to 3 nearby lymph nodes or into areas of fat near the lymph nodes but not to distant sites (T3 or T4a, N1/N1c, M0).

— or —

The cancer has grown into the muscularis propria or into the wall of the colon or rectum and has spread to 4 to 6 nearby lymph nodes but not to distant sites (T2 or T3, N2a, M0).

— or —

The cancer has grown into the submucosa and possibly the muscularis propria. It has spread to 7 or more nearby lymph nodes but not to distant sites (T1 or T2, N2b, M0).

Stage 3C

The cancer has grown through the wall of the colon or rectum, including the tissues lining it (the visceral peritoneum), but has not reached nearby organs. It has spread to 4 to 6 nearby lymph nodes but not to distant sites (T4a, N2a, M0).

— or —

The cancer has grown into the wall of the colon or rectum, including the visceral peritoneum, but has not reached nearby organs. It has spread to 7 or more nearby lymph nodes but not to distant sites (T3 or T4a, N2b, M0).

— or —

The cancer has grown through the wall of the colon or rectum and is attached to or has grown into nearby tissues or organs. It has spread to at least one nearby lymph node or areas of fat close to it but not to distant sites (T4b, N1 or N2, M0).

Stage 4A

The cancer has spread to one distant organ, such as the liver or lungs, or distant set of lymph nodes, but not to distant parts of the lining of the abdominal cavity, the peritoneum (any T, any N, M1a).

Stage 4B

The cancer has spread to more than one distant organ or distant set of lymph nodes, but not to distant parts of the peritoneum (any T, any N, M1b).

Stage 4C

The cancer has spread to distant parts of the peritoneum (any T, any N, M1c).

For colorectal cancers, available statistics are not based on the TNM cancer staging system. They are collected by the National Cancer Institute and put into the Surveillance, Epidemiology, and End Results (SEER) database. The SEER database separates colorectal cancer into three broader groups:

• Localized If the cancer has not spread outside of the colon or rectum, it is considered localized.
• Regional The cancer is outside the colon or rectum, but only to neighboring organs or lymph nodes.
• Distant The cancer is found in farther parts of the body, such as the liver or lungs.
  
  

Here’s how the TNM stages fit into the SEER groups:

Generally speaking, the more distant the cancer is from the colon or rectum, the poorer the prognosis.

• Localized: 91 percent
• Regional: 73 percent
• Distant: 13 percent
• Group average: 63 percent

For rectal cancer:

• Localized: 90 percent
• Regional: 74 percent
• Distant: 18 percent
• Group average: 67 percent

The Takeaway

• Colorectal cancer staging is crucial in understanding colon cancer progression, guiding treatment decisions, and assessing potential outcomes.
• Major tests used to stage colon cancer include CT scans, MRIs, ultrasounds, and PET scans to determine the spread of cancer to other body parts.
• Colorectal cancer at higher stages typically indicates a poorer prognosis, but every case is unique, so it's important to have ongoing conversations with your healthcare team for personalized care.
• Treatments for colorectal cancer have greatly improved over the past few decades, and so have survival rates with better understanding of the disease.