What You Need To Know About Colorectal Cancer — Image: CDC

Cells are the basic unit of all living things, and they are programmed to live, create new cells and then die. In cancer, cells lose this signal to die and continue to grow unrestrained in a disorderly manner, with the possibility of moving from one part of the body to the other. Colorectal cancer is the cancer of the colon, bowel and rectum. These are parts of the digestive system starts at the mouth and ends at the anus.

The digestive system is responsible for helping us break down food into smaller usable forms for nourishment and energy that is absorbed by the small intestines, as well as getting rid of waste products via the large intestine. The colon is the main part of the large intestine and has 4 other parts – ascending, transverse, descending, and sigmoid colon. The rectum is the last part of the colon where stools are stored before they are passed out via the anus. Any of these parts of the colon can be affected by cancer.

Who is affected?
Cancer is the second leading cause of death globally and was responsible for an estimated 9.6 million deaths in 2018, according to the World Health Organization (WHO). Around the world, about 1 in 6 deaths is due to cancer.
Colorectal cancer is the third most common cancer type globally with around 1.80 million cases and it caused 862,000 deaths at the end of 2018, the second-highest of all cancer deaths. While previously thought to be uncommon in Africa and Nigeria, colorectal cancer cases have been steadily rising in the past few years.

What causes colorectal cancer?
Most colorectal cancers develop from a polyp. A polyp is a growth in the lining of the digestive tract that is benign (non-cancerous) and causes no problems. Nearly 1 in 4 people over 50 have at least 1 polyp. However, a polyp can transform into cancer over 5 to 15 years. A cause for this transformation has not been found. There are some conditions (called risk factors) that can increase the odds of developing colorectal cancer. These include:

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Age greater than 60
Sedentary lifestyle
Family history of colorectal cancer
Prior colorectal cancer
Obesity
Excessive alcohol intake
Smoking
Race: Blacks and African-Americans may be at a higher risk of developing colorectal cancer.
Diabetes Mellitus
Diet rich in meat and fat but poor in fibre.
Other medical conditions like Ulcerative colitis, Crohn’s disease, Familial Adenomatous Polyp
History of other cancers, like breast, ovarian and endometrial cancers.

What are the symptoms seen in colorectal cancer?
Typically, the initial stages of cancer development do not cause any symptoms. As it grows, symptoms begin to develop. These are often based on the location of cancer, the size of the tumour (clump of cancer cells) and the overall health of the affected person. Initial symptoms include

- - Bleeding: This is the commonest symptom reported. It can be seen as darker coloured stools, blood mixed with stools or blood passed before or after stools. The quantity of blood passed is often small.
  - Change in bowel habit: You may see a deviation from your usual toilet habits, that is, diarrhoea or constipation.
  - Abdominal pain.
  - A feeling of not being able to empty the rectum.
As cancer progresses, other symptoms begin to show. These may include:
- - - Weight loss.
    - A general feeling of tiredness and fatigue.
    - Severe abdominal pain due to perforation.
    - Abdominal swelling due to blockage. This may result in bouts of vomiting.
    - Colorectal cancer may also cause other symptoms when it spreads to other structures, like the Live (yellowness of the eyes).
How is colorectal cancer diagnosed?
Doctors make the diagnosis of colorectal cancer after listening to the history of complaints, a physical examination and some investigations. Your doctor will perform a rectal exam to guide the diagnostic process and will order for blood and imaging tests. These will include a colonoscopy (a procedure with which a telescope is used to examine the colon), and a biopsy will be taken for further analysis. A computerised tomography scan may also be ordered.

How is colorectal cancer treated?
Treatment for colorectal cancer is aimed at either “curing” the patient, reducing the spread of cancer or controlling symptoms. This is based on the stage of cancer (degree of spread and affectation). Generally, treatment is offered via surgery, chemotherapy and radiotherapy. Surgery can be used to resect (cut out) the affected parts if it is discovered early.

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How can I prevent colorectal cancer?
- - - Eat a balanced diet with less meat and more fibre.
    - Quit smoking.
    - Exercise often. The daily target is around 30 minutes or 180 minutes weekly.
    - Maintain a healthy weight.
    - Drink alcohol in moderation.
    - Manage other health concerns promptly.
    - Get screened for colorectal cancer if you are 45 and above. If you have a family history of colorectal cancer, your doctor may ask you to screen earlier.