Colon cancer: symptoms, causes and treatment

The colon is the last part of the digestive tract, otherwise known as the large intestine. Colon cancer is a type of cancer that begins in the large intestine.

It can happen at any age but typically affects older adults. It usually begins as small collection of cells called polyps that form on the inside of the colon. Over time some of these polyps can become cancerous. Usually they are small and symptomless.

It is therefore advisable that if you are at risk you do regular screening so that the polyps can be identified and removed before they turn into cancer.

Many people with colon cancer experience no symptoms in the early stages of the disease. When symptoms appear, they’ll likely vary, depending on the cancer’s size and location in your large intestine.

If you notice any persistent symptoms that worry you, make an appointment with your doctor. There are no defined causes of colon cancer. The cancer develops when healthy cells in the colon develop changes (mutations) in their DNA.

The progression and spread of cancer cells

When the DNA is damaged it becomes cancerous, because the cells continue to divide even when new cells are not needed.

The cells then accumulate and form a tumour. With time, the cancer cells can grow to invade and destroy normal tissue nearby.

The cancerous cells can also travel to other parts of the body to form deposits there.

From around the age of 45, it is recommended that people consider colon cancer screening. People with a high risk should screen sooner and regularly.

Symptoms

Signs of colon cancer include:

• A change in bowel habits like diarrhoea or constipation.
• Rectal bleeding or blood in your stool.
• Abdominal cramps, gas or pain.
• Weakness or fatigue.
• Unexplained weight loss.

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Risk factors

Factors that may increase your risk of colon cancer include:

• Age – commonly in people older than 50.
• A previous history of polyps or cancer.
• Inflammatory bowel conditions like ulcerative colitis and Crohn’s disease.
• Inherited syndromes that increase colon cancer risk.
• Family history of colon cancer.
• Low-fibre, high-fat diet. Some studies have found an increased risk of colon cancer in people who have diets high in red and processed meat.
• A sedentary lifestyle. Getting regular physical activity may reduce your risk of colon cancer.
• Diabetes. People with diabetes or insulin resistance have an increased risk of colon cancer.
• Obesity
• Smoking. People who smoke may have an increased risk of colon cancer.
• Heavy use of alcohol.
• Radiation therapy directed at the abdomen to treat previous cancers increases the risk.

Prevention

To reduce the risk of colon cancer, you can take the following steps:

• Eat a variety of fruits, vegetables and whole grains.
• Drink alcohol in moderation, if at all.
• Stop smoking.
• Exercise most days of the week.
• Maintain a healthy weight by combining a healthy diet with daily exercise.

Treatment

The effectiveness of treatment will depend on the location of your cancer, its stage and your other health conditions. Treatment usually involves surgery. Other treatments, such as radiation therapy and chemotherapy, might also be recommended.

Surgery

If the cancer is small, your doctor may recommend a minimally invasive approach, such as removing polyps during a colonoscopy. Larger cancers will require more aggressive surgeries like colectomy, which is a removal of part of the colon.

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.

Lymph node removal. Nearby lymph nodes are usually also removed and tested for cancer. If your cancer is advanced or your overall health poor, your surgeon may recommend an operation to relieve your symptoms. This surgery isn’t to cure cancer, but instead to relieve signs and symptoms.

Chemotherapy

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. Chemotherapy may kill any cancer cells that remain in the body and help reduce the risk of cancer recurrence.

It might be used before an operation to shrink a large cancer so it’s easier to remove with surgery. It can be used to relieve symptoms that can’t be removed with surgery or cancer 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 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.

Immunotherapy

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 recognising the cancer cells. Immunotherapy works by interfering with that process. It is usually reserved for advanced colon cancer.

Supportive (palliative) care

Specialised 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 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. It is offered alongside curative or other treatments. Used alongside other appropriate treatments, people with cancer may feel better and live longer.

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