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Colorectal cancer is a disease affecting the colon and rectum in which cells in the either organ grow out of control. Colorectal cancer is also referred to as colon cancer.  The colon is approximately 5 feet (150 cm) long while the rectum is the last anatomic segment before the anus and is approximately 15cm in length.

What is Colorectal Cancer?

Colorectal cancer is a disease affecting the colon and rectum in which cells in the either organ grow out of control. Colorectal cancer is also referred to as colon cancer. The colon is approximately 5 feet (150 cm) long while the rectum is the last anatomic segment before the anus and is approximately 15cm in length.

As with other cancers, there are various grades and stages of colorectal cancer depending on its aggressiveness and whether it has spread to other organs.

Statistics indicate that in Malaysia colorectal cancer is the most common cancer in men and the second most common cancer in women. The incidence of this type of cancer increases with age; and males have a slightly higher risk of developing colorectal cancer. Interestingly, the incidence of colorectal cancer is highest among the Chinese for both sexes.

How does colorectal cancer start?

The majority of colorectal cancers start as a growth on the inner lining of the colon or rectum. These growths are called polyps. Although some polyps can change into cancer over time (usually over the course of many years), not all polyps become cancer. The chance of a polyp turning into cancer depends very much on the type of polyp that is discovered during screening as well as pathological examination of the polyp (adenomatous, serrated or hyperplastic). Both adenomatous and serrated polyps have a chance of turning into cancer while hyperplastic polyps are benign with no malignant potential.

Most colorectal cancers are adenocarcinomas. When cancer develops from a polyp, it grows or penetrates through the wall of the colon or rectum over time. The wall of the colon and rectum is made up of many layers – similar to an onion. Colorectal cancer begins in the innermost layer (the mucosa) and grows outwards through the layers.

How does colorectal cancer spread?

Cancer cells can grow into blood vessels or lymph vessels (tiny channels within the bowel) and thereafter can spread to nearby lymph nodes or other parts of the body. The stage and extent of spread of colorectal cancer depends on how deeply it grows into the wall of the colon and if it has spread outside the colon or rectum.

Local invasion relates to the extent that the cancer penetrates the bowel wall and into neighboring organs. For example, a person could have colorectal cancer involving the sigmoid colon or rectum that has invaded into the bladder signaling a spread. On the other hand, distant spread relates to metastases to other organs such as such as the liver or lungs.

What causes colorectal cancer?

There are several factors involved but the ultimate changes occur in the DNA of our cells. DNA changes or mutations can cause cells to grow out of control and the expression or suppression of certain genes can lead to tumour formation.

Although some DNA mutations are inherited, only a very small percentage of colorectal cancers are caused by inherited gene mutations. The majority of colorectal cancers are acquired gene mutations meaning that they occur at a particular period during a person’s lifetime and are not passed on to their children.

What are the symptoms of colorectal cancer?

As with all cancers, early detection is key in identifying and treating colorectal cancer before it has spread. If you are concerned, here are some symptoms to look out for:

  • Altered bowel habit such as unexplained constipation and diarrhoea or passage of loose stools that is persistent
  • Rectal bleeding
  • Passage of mucus
  • Anergia or low energy levels
  • Unexplained weight loss
  • Abdominal pain - persistent abdominal discomfort, such as cramps or distension and bloating
  • A feeling that your bowel doesn't empty completely
What are colorectal cancer risk factors?

There are a number of risk factors that may predispose a person towards an increased risk of developing colorectal cancer. This includes:

  • Diet – particularly diets with a high consumption of red meat and processed food.
  • Obesity
  • Sedentary or inactive lifestyle
  • Smoking
  • Alcohol consumption
  • Background of inflammatory bowel disease such as Crohn’s disease or ulcerative colitis.
  • Diabetes
  • Inherited syndromes - certain gene mutations passed through family generations
  • Family history of colon cancer - The risk of developing colorectal cancer increases if a blood relative has had the disease and is even greater if more than one family member was diagnosed with it
The Link between Colorectal Cancer and Diabetes

Several epidemiological studies have shown that individuals with type 2 diabetes have a higher risk of developing colorectal cancer. It has been hypothesised that elevated insulin levels due to insulin resistance and hyperinsulinemia - which occur in early stages of Type 2 diabetes – are potentially correlated with colorectal cancer in individuals with this type of diabetes. Another potential link between Type 2 diabetes and cancer is hyperglycaemia, which can impair the effectiveness of the immune system.

How important is a colonoscopy?

Colorectal cancer screening typically begins at age 50 but if you have a family history of colorectal cancer or a history of chronic inflammatory bowel disease (ulcerative colitis or Crohn's Disease), then screening should begin at age 40 or perhaps even earlier. Screening is highly effective. Colonoscopy plays an important role in colorectal cancer detection and is generally considered the preferred screening test. Colonoscopy can actually prevent the development of colorectal cancer because pre-cancerous polyps can be detected and removed during the same exam when they are discovered.

Colonoscopy enables visual inspection of the entire large bowel from the distal rectum to the cecum. It remains the gold standard for the detection of polyps and colorectal cancer. The technology for colonoscopy has evolved to provide a very clear image of the mucosa through a video camera attached to the end of the scope.

How can colorectal cancer be prevented?

You can help prevent colorectal cancer by practicing the following healthy habits:

  • Eat a healthy balanced diet; one that is rich in fiber with an emphasis on fruits and vegetables and whole grains.
  • Avoid red meat and processed food and over consumption of charred or barbecued meat.
  • Avoid a sedentary lifestyle by exercising regularly
  • Abstaining from smoking and recusing consumption of alcohol
  • Conducting screening tests as necessary.

If you notice any changes in your bowel behaviour or if you have any of the symptoms of colorectal cancer, please consult one of our specialists.

For more information please get in touch with our colorectal cancer surgeons by clicking the link below

Gleneagles Hospital Kuala Lumpur
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