Stages of Colon Cancer Explained

Have you or someone you know been diagnosed with colon cancer?  If so, one of the first things that the doctor will want to determine is the stage of the cancer.

Staging is a unique way of describing the local extent of the cancer and how far it has spread to other organs in the body. This process is critical because it helps the doctor determine the best treatment option.

Different diagnostic tests are used to establish the stage of cancer. There are also different stage descriptions for various types of cancer. In this article, we focus on colon cancer staging.

Staging of Colon Cancer

Colon cancer is staged based on the TNM staging system created by the American Joint Committee on Cancer. Your doctor will use the results from the diagnostic tests and scans performed to answer the following questions:

Tumour (T)

How far has the primary tumour grown into the wall of the colon or rectum?

Node (N)

Has the tumour spread to the neighbouring lymph nodes? If so, where and how much has it spread?

Metastasis (M)

Has the cancer tumour spread from your colon to other body parts such as the liver and lungs?  If so, where and how much has it spread?

Colon Cancer Stage Grouping

The five stages of colon cancer are as follows:

Stage 0

Stage 0 means your cancer has not grown beyond the innermost layer (mucosa) of the colon or rectum.

Stage 1

Stage 1 indicates that the cancer has extended beyond the innermost colon layer  (mucosa) to the next layers, referred to as submucosa or muscularis propria. However, it has not started to spread to the regional lymph nodes.

Stage 2

In stage 2, the cancer is a little bit advanced and has grown beyond both the mucosa and submucosa. Stage 2 can be classified into three distinct sub-stages, namely:

• 2A:  The cancer cells have not spread to regional lymph nodes or any other nearby tissue. It has only reached the outer layer of your colon.
• 2B: The cancer cells have not spread to the lymph nodes, but they have grown through the outer colon layer and to the visceral peritoneum (the membrane that holds the abdominal organs in place).
• 2C: The cancer cells have not spread to the lymph nodes but have grown to nearby body organs.

Stage 3

Stage 3 colon cancer can be classified as 3A, 3B, and 3C.

• 3A means the primary tumour has grown through the muscular layers of your colon into the nearby lymph nodes. However, it has not spread to distant body organs.
• 3B means the primary tumour has started to penetrate the visceral peritoneum. The cancer cells can be found in one to three lymph nodes and have not started to invade nearby body organs. It can also mean the tumour has not penetrated through the outer colon layers but can be found in at least four lymph nodes.
• 3C means the primary tumour has grown beyond the muscular layers, and cancer cells can be found in at least four nearby lymph nodes. Alternatively, the cancer has grown through the wall and invade nearby tissue or organ and has spread to at least one lymph node.

Stage 4

Stage 4 colon cancer is divided into two sub-stages, namely:

• 4A: This stage means the cancer cells have spread to at least one distant body organ such as the liver or distant set of lymph nodes.
• 4B: The cancer cells have spread to more than two distant body or distant set of lymph nodes.
• 4C: The cancer cells have spread to the distant parts of the peritoneum (the lining of the abdominal cavity)

Low-Grade vs High-Grade

In addition to conventional staging, colon cancer can also be classified as either low-grade or high-grade.

Typically, when a pathologist examines cancer cells, they assign a number that ranges between one and four depending on how healthy the cells look.

The higher the grade, the more abnormal the cells look.  In most cases, low-grade cancer grows slower than high-grade cancer. People who have low-grade cancer stand a better chance of recovery.

Tests to Diagnose and Stage Colon Cancer

Doctors may recommend a wide range of tests to diagnose colon cancer.  They also perform different tests to determine whether it has spread to other parts of the body. The following tests may be performed to diagnose colon cancer.

Blood tests

Although a blood test cannot reveal if you have colon cancer, your doctor will be looking for clues about your overall health.  He/she may also test your blood for chemical substances produced by colon cancer, such as carcinoembryonic antigens.

Blood tests will also measure the different types of cells in your blood. The blood cell count can reveal if you have anaemia because some people with colon cancer become anaemic as a result of the tumour bleeding.

Diagnostic colonoscopy

A diagnostic colonoscopy will only be done if you show symptoms or if something abnormal was found in another test.

A colonoscopy allows your doctor to examine the entire length of your colon or rectum to establish if there are any abnormalities.

The screening is done using a thin, flexible and lighted tube with a powerful video camera attached on one end.  The tube is usually inserted through the anus into your colon and rectum.

Biopsy

If your doctor suspects the presence of cancer cells during colonoscopy, he/she will recommend a biopsy. In a biopsy, a small piece of the colon/rectum tissue is extracted for examination.

A biopsy is the only way to make an accurate diagnosis of colon cancer.

Imaging tests

Imaging tests such as computed tomography scan, ultrasound, magnetic resonance imaging (MRI) scan or positron emission tomography (PET) scan use x-rays, magnetic fields or radioactive substances to generate clear images of internal body organs to help the doctor look for suspicious cancer growths or determine how far cancer has spread.

Colon Cancer Treatment by Stage

After examining your cancer and determining its stage, the doctor will recommend an appropriate course of treatment.

For stage 0 colon cancer, a polypectomy may be performed to get rid of all malignant cells. If the cells have affected a much larger area, the doctor may perform a resection (a minor and minimally invasive surgery).

For stage 1 colon cancer, surgery is usually performed to remove the affected cells. The surgery is referred to as colectomy and involves rejoining the healthy parts of your rectum or colon.

Stage 2 colon cancer is still treated with surgery that gets rid of the affected areas. The surgery may be combined with chemotherapy to yield better results.

The treatment for all categories of stage 3 colon cancer involves surgery to remove the affected areas. Surgery is combined with chemotherapy, but your doctor may recommend radiation treatment if surgery is not suitable.

Lastly, stage 4 colon cancer is treated by various treatment options. Surgery may be performed to remove the primary tumour or small affected areas in distal body organ. Chemotherapy, immunotherapy, targeted therapy or radiation may be given based on patient’s condition.

Conclusion

Diagnosing colon cancer at the earliest stages offers you the greatest chance for recovery. Doctors generally recommend that individuals with an average risk of colon cancer begin screening at the age of 50.

If you are diagnosed with colon cancer, your doctor will perform several tests to determine its stage and recommend appropriate treatment options.

It is crucial to understand that many factors will determine your survival rate, including your cancer stage, overall health, age, and how you respond to treatment.