Colon cancer: Symptoms, Causes, Risk factors, Diagnosis Treatment and Prevention

Image showing a cartoon representation of a common location of colon cancer in the human large bowel.

Colon cancer: Location representation


When Adeniran Chukwuemeka (not the real name) died one year ago, his family - unusual for an African family, was gracious to disclose his cause of death. It was colon cancer (also commonly referred to as bowel cancer).


‘Niran died, aged 62. He was a doctor and distinguished public health specialist.

His family felt that disclosing his cause of death will help to raise awareness about colon cancer in the community he grew up in and worked.

According to ‘Niran’s wife, her husband had been complaining of irregular stooling, occasional tummy pains and seeing blood in stool off and on for well over a year prior to his death.

“He believed he had hemorrhoids and considered his busy work-life schedule were to blame for his complaints”, said ‘Niran’s wife.

Even for a doctor, it never crossed ‘Niran’s mind that his complaints could indicate a more serious ailment. So, he never sought medical attention until it was too late.

By the time ‘Niran eventually visited his doctor to complain, he had started having more frequent and troublesome abdominal pain. The sighting of blood in stool were more consistent and sometimes continuous.

Eventually, ‘Niran was diagnosed with colon cancer for the first time three months prior to his death.

At the time Niran was taken to surgery, it was discovered that he had very advanced stage colon (lower bowel) cancer that had spread to involve many organs in his abdomen and his bones.

‘Niran’s wife said: “His doctor said he had stage IV colon cancer and surgery was suspended. Supportive medical treatment was substituted. He became poorly rapidly soon thereafter.”

“My husband’s doctor told me after his death, that ‘Niran could have been saved from bowel cancer if he had come up with his complaints several years ago”, said ‘Niran’s wife.

“I urge everyone, male or female, in mid-life stage with history of any bowel complaints to get a doctor’s checkup promptly and early”.

“Early detection could have saved my husband”, she said.


What is colon (or colorectal) cancer?

Colon cancer is a type of cancer that begins in the large intestine (colon). About 65% of colon cancers occur in the rectum/sigmoid colon area and 15% in the ascending colon (see illustration). The colon and its different parts form the final part of the digestive tract.

Image showing different parts of the colon.

Image showing different parts of the colon. Any part can be affected by colon cancer, but the recto-sigmoid colon is affected most. Image credit: Mayo Clinic


In Sub-Sahara Africa, colon cancer is considered to be the 5th commonest cancer with an estimated incidence rate of 4.04 per 100 000 population (4.38 for men and 3.69 for women).1 This is very likely an under-estimation.

Colon cancer typically affects older adults, though it can occur at any age. It usually begins as a small, noncancerous (benign) growth of cells called polyps that form on the inside of the colon. Over time some of these polyps can become colon cancers.

Polyps may be small and produce few, if any, symptoms. For this reason, doctors recommend regular screening tests to help prevent colon cancer by identifying and removing polyps before they turn into cancer.


What are the early symptoms of bowel cancer?

As in the case of ‘Niran, the symptoms of bowel cancer can often be subtle and don’t necessarily make you feel ill.

More than 90 per cent of people that are diagnosed with bowel cancer will have one or more of the following symptoms:

  • Noticeable change in bowel habit – stooling more often, with looser, runnier stool that may sometimes be accompanied with tummy (abdominal) pain.
  • Blood in the stool - without other symptoms of piles (haemorrhoids) – this makes it unlikely the cause is haemorrhoids
  • Abdominal pain, discomfort or bloating always brought on by eating – sometimes resulting in a reduction in the amount of food eaten and weight loss
  • Weakness or fatigue
  • Unexplained weight loss
  • Constipation, where you pass harder stools less often, is rarely caused by serious bowel conditions.

Most people with these symptoms may not have bowel cancer.


When should you see a doctor?

If you experience one of more of these symptoms and they persist for more than four weeks, you are best advised to visit your doctor.


What causes colon cancer?

The cause of colon cancer is not known. In general colon cancer like most other cancers start when healthy cells develop abnormal changes (mutation) in their DNA. A cell’s DNA contains a set of instructions that tells the cells what to do.

In colon cancer, tansformative mutation is believed to occur in non-cancerous small tissues (polyps) that grow inside the inner lining of the large bowel (colon). If not detected early and removed, the polyps will become cancerous, spread beyond the colon and may eventually be a cause of death.


Who is at risk?

While the exact cause of bowel cancer is unknown, there are a number of factors that can increase your risk, including:

  • Age – almost nine in 10 cases of bowel cancer occur in people aged 60 or over.
  • Diet – a diet high in red or processed meats and low in fibre can increase your risk.
  • Previous personal history of polyps or colon cancer.
  • Previous personal history of chronic inflammatory bowel disease, e.g., Ulcerative colitis and Crohn disease.
  • Weight – bowel cancer is more common in people who are overweight or obese.
  • Diet – bowel cancer has been associated with a typical western-style diet that is low in fibre, high in fat and calories.
  • Diabetes - people with diabetes are known t o have higher risk of developing colon cancer.
  • Exercise – being inactive increases your risk of getting bowel cancer.
  • Alcohol and smoking – a high alcohol intake and smoking may increase your chances of getting bowel cancer.
  • Family history – having a close relative who developed bowel cancer under the age of 50 puts you at a greater lifetime risk of developing the condition. Screening is offered to people in this situation, and you should discuss this with your doctor.
  • Radiation therapy – previous radiation therapy directed at the abdomen to treat previous cancer of whatever type, increases the risk of developing colon cancer.


Colon cancer: How is it diagnosed?

If you experience one of more of the symptoms that may indicate colon cancer and they persist for more than four weeks, you are best advised to visit your doctor.

Your doctor will take a full history from you and may decide to:

  • Carry out a simple examination of your tummy and bottom (rectum) to make sure you have no lumps.
  • Arrange for a simple blood test to check for anaemia (low blood iron level) – this can confirm whether there’s any bleeding from your bowel that you haven’t een aware of.
  • Use a special equipment (scope) to examine the inside of your colon (colonoscopy). Colonoscopy uses a long, flexible and slender tube attached to a video camera and monitor to view your entire colon and bottom (rectum). If any suspicious areas are found, your doctor can pass surgical tools through the tube to take tissue samples (biopsies) for analysis and remove polyps.

It is recommended that you start colonoscopy from age 45 to 50 years and probably earlier if you have a family history of the condition. Thereafter, colonoscopy is recommended every 10 years.  

Image showin procedure for colonoscopy with colonoscope in large bowel.

Colonoscopy: During a colonoscopy, the doctor inserts a colonoscope into your rectum to check for abnormalities in your entire colon. Image credit: Mayo Clinic.


  • Arrange for you to have additional blood and other tests in hospital to make sure there’s no serious cause of your symptoms. For example, your doctor may test your blood for a chemical sometimes produced by colon cancers (carcinoembryonic antigen, or CEA). Tracked over time, the level of CEA in your blood may help your doctor understand your prognosis and whether your cancer is responding to treatment.



Determining the extent of your cancer?

If you've been diagnosed with colon cancer, your doctor may recommend tests to determine the extent (stage) of your cancer. Staging helps determine what treatments are most appropriate for you.

In many cases, the stage of your cancer may not be fully determined until after colon cancer surgery, but tests used in staging may include imaging procedures such as abdominal, pelvic and chest CT scans.

Colon cancer staging: At its earliest stage (stage 0), colon cancer is limited to the inner lining of your colon. As colon cancer progresses, it can grow through your colon and extend to nearby structures. The most advanced stage of colon cancer (stage IV) indicates cancer has spread to other areas of the body, such as the liver or lungs. Image credit: Mayo Clinic


The stages of colon cancer are indicated by Roman numerals that range from 0 to IV, with the lowest stages indicating cancer that is limited to the lining of the inside of the colon. By stage IV, the cancer is considered advanced and has spread (metastasized) to other areas of the body.


Treatment of colon cancer

Treatment options offered for colon cancer varies with the location of the cancer, the stage of the disease and other co-existing medical conditions at time of diagnosis.

Generally, treatment for colon cancer usually involves surgery to remove the cancer. Other treatments, such as radiation therapy and chemotherapy, might also be recommended.


Surgery for early-stage colon cancer

If your colon cancer is very small, your doctor may recommend a minimally invasive approach to surgery, such as:

  • Removing polyps during a colonoscopy (polypectomy). If your cancer is small, localized, completely contained within a polyp and in a very early stage, your doctor may be able to remove it completely during a colonoscopy.
  • Endoscopic mucosal resection. Larger polyps might be removed during colonoscopy using special tools to remove the polyp and a small amount of the inner lining of the colon in a procedure called an endoscopic mucosal resection.
  • Minimally invasive surgery (laparoscopic surgery). Polyps that can't be removed during a colonoscopy may be removed using laparoscopic surgery. In this procedure, your surgeon performs the operation through several small incisions in your abdominal wall, inserting instruments with attached cameras that display your colon on a video monitor. The surgeon may also take samples from lymph nodes in the area where the cancer is located.


Surgery for more advanced colon cancer


If the cancer has grown into or through your colon, your surgeon may recommend any of the following surgeries depending on your particular situation:


Partial colectomy. showing resected area of colon (sigmoid) containing the cancer along with margin of normal tissue on either side. sigmoi colon. When the free margins are not sewn back immediately, an ostomy is commonly created to serve as temporay evacuation for stool. Image credit: Mayo Clinic.


  • Partial colectomy. During this procedure, the surgeon removes the part of your colon that contains the cancer, along with a margin of normal tissue on either side of the cancer. Your surgeon is often able to reconnect the healthy portions of your colon or rectum. This procedure can commonly be done by a minimally invasive approach (laparoscopy) or through open abdominal surgery (laparotomy).
  • Surgery to create a way for waste to leave your body. When it's not possible to reconnect the healthy portions of your colon or rectum, you may need an ostomy. This involves creating an opening in the wall of your abdomen from a portion of the remaining bowel for the elimination of stool into a bag that fits securely over the opening.

Sometimes the ostomy is only temporary, allowing your colon or rectum time to heal after surgery. In some cases, however, the colostomy may be permanent.

  • Lymph node removal. Nearby lymph nodes are usually also removed during colon cancer surgery and tested for cancer.


Surgery for advanced cancer

  • If your cancer is very advanced or your overall health very poor, your surgeon may recommend an operation to relieve a blockage of your colon or other conditions in order to improve your symptoms. This surgery isn't done to cure cancer, but instead to relieve signs and symptoms, such as a blockage, bleeding or pain.
  • In specific cases where the cancer has spread only to the liver or lung but your overall health is otherwise good, your doctor may recommend surgery or other localized treatments to remove the cancer. Chemotherapy may be used before or after this type of procedure. This approach provides a chance to be free of cancer over the long term.



  • Chemotherapy uses drugs to destroy cancer cells. Chemotherapy for colon cancer is usually given after surgery if the cancer is larger or has spread to the lymph nodes. In this way, chemotherapy may kill any cancer cells that remain in the body and help reduce the risk of cancer recurrence.
  • Chemotherapy might also be used before an operation to shrink a large cancer so that it's easier to remove with surgery.
  • Chemotherapy can also be used to relieve symptoms of colon cancer that can't be removed with surgery or that has spread to other areas of the body. Sometimes it's combined with radiation therapy.


Radiation therapy

  • Radiation therapy uses powerful energy sources, such as X-rays and protons, to kill cancer cells. It might be used to shrink a large cancer before an operation so that it can be removed more easily.
  • When surgery isn't an option, radiation therapy might be used to relieve symptoms, such as pain. Sometimes radiation is combined with chemotherapy.


Targeted drug therapy

  • Targeted drug treatments focus on specific abnormalities present within cancer cells. By blocking these abnormalities, targeted drug treatments can cause cancer cells to die.
  • Targeted drugs are usually combined with chemotherapy. Targeted drugs are typically reserved for people with advanced colon cancer.



  • Immunotherapy is a drug treatment that uses your immune system to fight cancer. Your body's disease-fighting immune system may not attack your cancer because the cancer cells produce proteins that blind the immune system cells from recognizing the cancer cells. Immunotherapy works by interfering with that process.
  • Immunotherapy is usually reserved for advanced colon cancer. Your doctor might have your cancer cells tested to see if they're likely to respond to this treatment.


Supportive (palliative) care

  • Palliative care is medical care that focuses on providing relief from pain and other symptoms of a serious illness. Palliative care is provided by a team of doctors, nurses and other specially trained professionals that work with you, your family and your other doctors to provide an extra layer of support that complements your ongoing care.
  • Palliative care teams aim to improve the quality of life for people with cancer and their families. This form of care is offered alongside curative or other treatments you may be receiving.
  • When palliative care is used along with all of the other appropriate treatments, people with cancer may feel better and live longer.


Prevention of colon cancer

Screening colon cancer

In addition to minimising risk factors for colon cancer, screening and early detection of pre-cancerous polyps is at the heart of prevention of colon cancer.

It is recommended that people with an average risk of colon cancer consider colon cancer screening around age 50. But those with an increased risk, such as those with a family history of colon cancer, should consider screening sooner.

Several screening options exist — each with its own benefits and drawbacks. Talk about your options with your doctor, and together you can decide which tests are appropriate for you.

Lifestyle changes to reduce your risk of colon cancer

You can take steps to reduce your risk of colon cancer by making changes in your everyday life. Take steps to:

  • Eat a variety of fruits, vegetables and whole grains. Fruits, vegetables and whole grains contain vitamins, minerals, fiber and antioxidants, which may play a role in cancer prevention. Choose a variety of fruits and vegetables so that you get an array of vitamins and nutrients.
  • Drink alcohol in moderation, if at all. If you choose to drink alcohol, limit the amount of alcohol you drink to no more than one drink a day for women and two for men.
  • Stop smoking. Talk to your doctor about ways to quit that may work for you.
  • Exercise most days of the week. Try to get at least 30 minutes of exercise on most days. If you've been inactive, start slowly and build up gradually to 30 minutes. Also, talk to your doctor before starting any exercise program.
  • Maintain a healthy weight. If you are at a healthy weight, work to maintain your weight by combining a healthy diet with daily exercise. If you need to lose weight, ask your doctor about healthy ways to achieve your goal. Aim to lose weight slowly by increasing the amount of exercise you get and reducing the number of calories you eat.


Colon cancer prevention for people with a high risk

Some medications have been found to reduce the risk of precancerous polyps or colon cancer. For instance, some evidence links a reduced risk of polyps and colon cancer to regular use of aspirin or aspirin-like drugs. But it's not clear what dose and what length of time would be needed to reduce the risk of colon cancer. Taking aspirin daily has some risks, including gastrointestinal bleeding and ulcers.

These options are generally reserved for people with a high risk of colon cancer. There isn't enough evidence to recommend these medications to people who have an average risk of colon cancer.

If you have an increased risk of colon cancer, discuss your risk factors with your doctor to determine whether preventive medications are safe for you.



Bottom line, colon (colorectal) cancer is the fifth commonest cancer in Sub-Saharan Africa. Men are slightly more at risk than women. Any age group from young adulthood may be affected, bit it is commonest from age 60 and above. Symptoms of colon cancer are non-specific and may be characterized by abdominal pain, blood in stool or rectal bleeding, fatigue, weakness and unexplained eight loss. Early presentation to your doctor helps early detection and better treatment options. Prevention of colon cancer calls for reduction of risk factors and yearly screening of at risk individuals.



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Published: February 22, 2020

Updated: May 27, 2024.

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