Colon Cancer

In this article

Identify the colon What is colon cancer? What are the symptoms? How colon cancer is diagnosed? Staging Stage TNM staging system Grading Treatment overview Surgery Chemotherapy Targeted therapy How treatment is planned Treatment goals according to the stage Treatment with curative intent Open or laparoscopic surgery Stomas (colostomy/ileostomy) Treatment for advanced colon cancer Chemotherapy Liver resection Lung resection Treating a blocked bowel (bowel obstruction) Aftermath

Identify the colon

Colon is the part of the bowel after the small intestine. This runs from right side to the top of the abdomen and then towards theft and then downwards to the pelvis to join the rectum. This is also called the large bowel due to the larger diameter of the lumen compared to the small bowel. Its about one and a half meters long. Its divided in to four parts:

Caecum & Ascending colon

The  first part of the colon starts at the bottom, right-hand side of your abdomen. It comes just after the small bowel. It goes up the right side of the abdomen.

Transverse colon

The second section goes across the abdomen from your right to your left side.

Descending colon

The third section goes down the left-hand side of your abdomen.

Sigmoid colon

The  final part of the colon is an ‘S’ shape bend that joins onto the rectum.

The walls of the colon are made up of four layers of body tissue. Most colon cancers start in the inner lining of the bowel and commonly starts as small growths called polyps.

What is colon cancer?

Most commonly, a cell within the inner lining of the colon becomes abnormal. It stops  listening to the instruction given to them about control of cell division, cell growth and cell death. These abnormal cells keeps dividing making more and more abnormal cells. These eventually form a tumour / lump that will expand in to the lumen, along the wall around the lumen, and towards out side from the bowel wall.

These tumours will have very abnormal and fragile blood vessels which will cause bleeding in to the lumen. These tumours are solid and rigid thus limiting bowel wall expansion when necessary therefore will cause constipation / obstruction. When they spread outside the bowel wall, they may invade other organs/structures in the vicinity. Also, they have the potential to detach from the primary tumour and enter the blood stream or lymphatic stream to travel to a far-away place to give rise to another secondary tumour making the eradication of the cancer much harder.

What are the symptoms?

The symptoms of colon cancer may include:

  • blood in, or on, your stools (bowel motions) – the blood may be bright red or dark
  • a change in your normal bowel habit, such as diarrhoea or constipation, that happens for no obvious reason and lasts longer than three weeks
  • unexplained weight loss
  • pain in the tummy (abdomen) or back passage
  • feeling that you haven’t emptied your bowel properly after a bowel motion
  • unexplained tiredness
  • Sometimes, the cancer can cause a blockage (obstruction) in the bowel. The person may feel constipated and bloated, be sick (vomit) and have tummy pain with tummy distention.

Although these symptoms can be caused by conditions other than colon cancer, you should always have them checked by your doctor.

If you have symptoms that don’t improve within a few weeks, or if your symptoms get worse, it’s important that you’re referred to a specialist for tests to find out what the problem is.

How colon cancer is diagnosed?

Sometimes, its diagnosed when you come with symptoms. Sometimes, its diagnosed only after being admitted to hospital with a problem, such as bowel obstruction.

If you come with symptoms,

You will be asked about your general health and any previous medical problems you’ve had. You’ll be asked whether you have a family history of bowel cancer.

During the examination, you will get a rectal examination. This involves placing a gloved finger into your back passage to feel for any lumps or swelling.

You will usually have a blood test to check your level of red blood cells and haemoglobin. If you have a low number of red blood cells or low haemoglobin levels, this is called anaemia. You will also have blood tests to check whether your liver and kidneys are working normally.

Then the specific tests to diagnose the cancer will be done. The main test used to look for bowel cancer is a colonoscopy. Other tests that are sometimes used are virtual colonoscopy / CT colonogram or sigmoidoscopy.

During the colonoscopy, there tumour would be visible and it will be possible to take a small piece from it for the biopsy.

The biopsy will confirm whether its cancer - the definitive /confirmed diagnosis.


Once the diagnosis is confirmed, it is necessary to find out the size and position of the cancer and whether it has spread in order to plan the appropriate treatment. This involves doing some more tests. These are to This is called staging.

Staging Contrast CT (computerised tomography) scan

This test checks for any signs that the cancer has spread outside the colon. A Contrast CT scan is done after you were given a drink or while you are getting an injection of a dye (provided that you are not allergic to it), which allows particular areas to be seen more clearly. A CT scan takes a series of x-rays, which build up a three- dimensional picture of the inside of the body. The scan takes 10–30 minutes and is painless. It uses a small amount of radiation, which is very unlikely to harm you and will not harm anyone you come into contact with.

Some people also have a PET/CT scan. This is a combination of a CT scan (see above) and a positron emission tomography (PET) scan. A PET scan uses low-dose radiation to measure the activity of cells in different parts of the body. A PET/CT scan may occasionally be done if more detailed information is needed after a CT scan. It may also be used to plan treatment if there is cancer in the liver or lungs.

Blood tests

Apart from the blood tests to assess your general health, blood may be tested for a protein called carcinoembryonic antigen (CEA). Some people with bowel cancer have higher levels of this protein. If your level of CEA is high, it can be used to check regularly to see the effectiveness of the treatment.

MRI (magnetic resonance imaging) scan

An MRI scan can help doctors plan treatment if there is cancer in the liver.


The stage of a cancer describes its size and whether it has spread. Knowing the stage of your cancer helps to decide on the best treatment for you. The most commonly used staging system is the TNM system.

TNM staging system

  • T describes how far the tumour has grown into the wall of the bowel, and whether it has grown into nearby tissues or organs.
  • N describes whether the cancer has spread to the lymph nodes.
  • M describes whether the cancer has spread to another part of the body such as the liver or lungs (secondary or metastatic cancer).

T – Tumour

  • The bowel wall is made up of layers of different tissues.
  • Tis means the cancer is at its earliest stage (in situ). It is growing into the mucosa but no further.
  • T1 means the tumour is only in the inner layer of the bowel (submucosa).
  • T2 means the tumour has grown into the muscle layer of the bowel wall but no further.
  • T3 means the tumour has grown into the outer lining of the bowel wall (serosa) but no further.
  • T4 means the tumour has grown through the outer layer of the bowel wall (serosa) and through the membrane covering the outside of the bowel wall (peritoneum).
  • T4a means it has grown into other nearby structures, such as other parts of the bowel or other organs or body structures.
  • T4b means the tumour has caused a hole in the bowel wall (perforation) and cancer cells have spread outside the bowel.

N – Nodes

  • N0 means no lymph nodes contain cancer cells.
  • N1 means there are cancer cells in up to three nearby
  • lymph nodes.
  • N2 means there are cancer cells in four or more nearby lymph nodes.

M – Metastases

  • M0 means the cancer hasn’t spread to distant organs.
  • M1 means the cancer has spread to distant organs such as the liver or lungs.

Number staging system

Information from the TNM system can be used to give a number stage from 0 to 4.

  • Stage 0 – The cancer is at its earliest stage and is only in the mucosa (Tis N0 M0).
  • Stage 1 – The cancer has grown into the submucosa or muscle but has not spread to the lymph nodes or elsewhere (T1 N0 M0 or T2 N0 M0).
  • Stage 2 – The cancer has grown through the muscle wall or through the outer layer of the bowel, and may be growing into tissues nearby. The cancer has not spread to the lymph nodes or elsewhere (T3 N0 M0 or T4 N0 M0).
  • Stage 3 – The tumour is any size and has spread to lymph nodes nearby, but has not spread anywhere else in the body (Any T N1 or N2 M0).
  • Staging and grading 29
  •  Stage 4 – The tumour is any size. It may have spread to nearby lymph nodes. The cancer has spread to other parts of the body such as the liver or lungs (Any T Any N M1).


The grade of a cancer gives doctors an idea of how quickly it may develop. Doctors will look at a sample of the cancer cells under a microscope to find the grade of your cancer.

  1. Grade 1 (low-grade) – The cancer cells tend to grow slowly and look quite similar to normal cells (they are ‘well differentiated’). These cancers are less likely to spread than higher grade cancers.
  2. Grade 2 (moderate-grade) – The cancer cells look more abnormal.
  3. Grade 3 (high-grade) – The cancer cells tend to grow more quickly and look very abnormal (they are ‘poorly differentiated’). These cancers are more likely to spread than low-grade cancers.

Treatment overview

Treatments used for colon cancer include surgery, chemotherapy and targeted therapy. Often, a combination of treatments is used.

Treatment depends on the stage of the cancer and where it is in the colon. It also depends on your general health and personal preferences.

It’s important that you have the chance to discuss treatment options. This will help you understand why a particular plan of treatment has been suggested, and how the treatment may affect you.


Surgery to remove the cancer is one of the main treatments for colon cancer. The operation usually involves removing the affected part of the colon as well as nearby lymph nodes. If the cancer has grown into tissue or organs nearby, its necessary to remove parts of these too.

Sometimes, surgery is used to relieve symptoms rather than cure the cancer. This may be if the cancer is causing a blockage in the bowel. Especially when its impossible to remove the cancer entirely.

Occasionally, surgery may be used to remove cancer that has spread to a distant part of the body, such as the liver or lungs.


Chemotherapy may be given before or after surgery to reduce the risk of the cancer coming back. It can also be used as the main treatment for a cancer that has spread or that can’t be removed by surgery. The aim is to control the cancer for as long as possible. Chemotherapy may be used to shrink cancer and relieve symptoms if the cancer has come back after treatment, or if it has spread.

Targeted therapy

Targeted therapies are sometimes used on their own or in combination with chemotherapy to control secondary cancer.

How treatment is planned

A team of specialists will discuss to plan your treatment. This multidisciplinary team (MDT) will include a:

  • surgeon who specialises in bowel cancers
  • clinical oncologist (radiotherapy and chemotherapy specialist)
  • radiologist (specialist in CT MRI and PET scans)
  • pathologist (specialist in studying tissue samples to detect diseases)
  • stoma care nurse

Treatment goals according to the stage

These may be
  • to try to cure the cancer
  • to help you live longer or
  • to relieve symptoms

Treatment with curative intent


Surgery is the most common treatment for colon cancer. A surgeon who specialises in treating bowel cancer should do it. The type of surgery you have will depend on the stage of the cancer and where it is in the bowel. Your doctor will discuss this with you.

Surgery to remove colon cancer

Local resection

Very early-stage colon cancers can sometimes be removed using an operation called local resection. The surgeon will remove the cancer from the lining of the bowel using a colonoscope. A pathologist will examine the cancer that’s been removed. If it’s found to be high-grade, your surgeon may recommend that you have a second operation. This is to remove more of the colon to make sure that no cancer cells are left behind.

Removing part or all of the colon

During this kind of surgery, the piece of bowel that contains the cancer is removed. The two open ends are then joined together. The join is known as an anastomosis. The lymph nodes near the colon are also removed, because this is usually the  first place the cancer spreads to.

Removing half of the colon is called a hemi-colectomy. Either the left side or the right side may be removed, depending on where the cancer is. In a left hemi-colectomy, the left half of the transverse colon and the descending colon is removed. In a right hemi-colectomy, the right half of the transverse colon and the ascending colon is removed. Some people have an operation to remove the sigmoid colon, called a sigmoid colectomy. Some people have their transverse colon removed, called a transverse colectomy.

Removing the whole colon is called a total colectomy.

Open or laparoscopic surgery

Your operation may be carried out as open surgery or as laparoscopic (keyhole) surgery. Open surgery means the surgeon makes one large cut (incision). Afterwards, you have a wound that goes down in a line from just below your breastbone (sternum) to just below the level of your tummy button (navel). Some people have a wound that goes across their tummy instead.

In laparoscopic (keyhole) surgery, the surgeon makes four or five small cuts in the abdomen rather than one big cut. They pass a laparoscope into the abdomen through one of the cuts. A laparoscope is a thin tube containing a light and camera. Then they pass specially designed surgical tools through the other cuts to remove the cancer. Recovery from laparoscopic surgery is usually quicker than recovery from open surgery.

Stomas (colostomy/ileostomy)

After an operation to remove colon cancer, some people will go to the toilet in a different way. They will have an opening on their tummy wall through which they pass bowel motions. This is called a stoma. A bag is worn over the stoma to collect bowel motions.

The stoma is made from an opening in part of the bowel. If the stoma is made from an opening in the colon it is called a colostomy. If it’s made from an opening in the small bowel (ileum) it is called an ileostomy.

Stomas can be temporary or permanent. Only a small number of people with colon cancer need a permanent stoma.A temporary stoma is made to allow the bowel to rest after colon cancer surgery. If you have a temporary stoma, you will usually have a second smaller operation a few months later to close the stoma and rejoin the bowel. This operation is called a stoma reversal.

Treatment for advanced colon cancer

Advanced colon cancer is where there are either liver or lung metastasis present at the time of the diagnosis. Also includes those cases where the primary tumour is so advanced that it invades other structures and cannot be safely removed completely.


If colon cancer has spread to the liver, the most common treatment is chemotherapy. The aim is to shrink the cancer and to control it for as long as possible. Chemotherapy is prescribed by the oncologist. You will be per-assesed for the risks, the tumour stage and the grade in order to select the best regimen for you. Most common regimen prescribed is FOLFOX.

Liver resection

Some people may be able to have surgery to remove the part of the liver affected by cancer. This operation is called a liver resection. Its usually done only if all the metastasis can be safely removed either from liver or lung. If you have metastasis anywhere in the body which cannot be removed, this option is not for you .

Liver resection is a major operation that takes 3–7 hours. This treatment is only suitable for a few people with secondary liver cancer. An operation to remove the cancer in the colon may be done at the same time of the liver resection or as a separate operation from the liver resection. A course of chemotherapy is usually given before. It can sometimes can lead to a cure.

Lung resection

The main treatment for cancer that has spread to the lungs is chemotherapy. But occasionally, people may be offered surgery to remove the affected part of the lung. This is only if the cancer is in just one area of the lung and nowhere else in the body.

Treating a blocked bowel (bowel obstruction)

Sometimes, colon cancer can narrow the bowel, stopping bowel motions from passing through. This can cause symptoms such as tummy pain, tummy distention and vomiting. It usually needs to be treated urgently. It can be treated in one of two ways.

Stenting to relieve a blocked bowel

The surgeon uses a colonoscope to insert an expandable metal tube (stent) into the blockage. The tube then expands to hold the bowel open. The cancer causing the blockage can usually be removed with an operation at a later date.

Surgery to relieve a blocked bowel

Sometimes, a bowel obstruction is treated with an operation to remove the blocked section of bowel. Most people will have a temporary or permanent stoma after this operation. The surgeon may remove the cancer at the same time or do this later in another operation.


Depending on the type of operation you’ve had, you’ll probably be ready to go home 3–7 days after surgery.

You’ll be given an appointment to attend an outpatient clinic for your post-operative check-up. At the appointment, you will be informed about whether you need to have any further treatment, such as radiotherapy or chemotherapy.