What is Colorectal / Colon Cancer?
Colorectal cancer, also known as colon cancer, rectal cancer or bowel cancer, is cancer of the colon (the longest part of the large intestine) or rectum (the last several inches of the large intestine before the anus). Colorectal cancers are mostly adenocarcinomas (cancers that begin in cells that produce mucus and other fluids).
There is no single cause of colorectal cancer, as in most cases, colon cancer begins as a polyp that develops into a cancerous growth. People with certain risk factors are more likely to develop colorectal cancer. The common risk factors for colorectal cancer are:
1. Colorectal Polyps
are growths on the inner wall of the colon or rectum commonly found in people
over the age of 50. While most polyps are benign (not cancer), some polyps
(adenomas) can become cancerous.
2. Ulcerative Colitis or Crohn’s Disease
A condition that causes inflammation of the colon, such as ulcerative colitis or Crohn’s disease, over many years can increase the risk of developing colorectal cancer.
3. Personal History of Cancer
A colorectal cancer survivor may develop colorectal cancer a second time. Women with a history of cancer of the ovary, uterus or breast are also at a higher risk of developing colorectal cancer.
4. Family History of Colorectal Cancer
A family history of colorectal cancer can indicate a higher risk of developing this disease, especially if a family member or relative suffered from the cancer at a young age.
5. Lifestyle Factors
People who smoke, or consume a diet that is high in fat and low in fruits and vegetables have a higher chance of developing colorectal cancer.
6. Age over 50
Colorectal cancer is more likely to occur to people over the age of 50. More than 90% of people with this disease are over the age of 50.
Common symptoms of colorectal cancer include:
- Change in bowel habits (diarrhoea or constipation)
- Feeling that your bowel does not empty completely
- Finding blood (either bright red or very dark) in your stools
- Finding your stools are narrower than usual
- Frequently having gas pains or cramps, or feeling full or bloated
- Losing weight with no known reason
- Feeling very tired all the time
- Having nausea or vomiting
Take note that these symptoms can be caused by other health problems and are often not due to cancer. Additionally, it is important to note that early stage cancer does not usually cause pain and may not have any notable symptoms. Therefore, anyone with these symptoms should see a doctor to be screened for colorectal cancer as early as possible.
Screening tests help your doctor find polyps or cancer before you have symptoms. Early detection of colorectal cancer will also improve effectiveness of cancer treatment. The following screening tests can be used to detect polyps, cancer, or other abnormalities.
Faecal Occult Blood Test (FOBT)
Cancer or polyps can sometimes cause bleeding, and the FOBT can detect tiny amounts of blood in the stool. If blood is detected in the stools, other tests can be carried out to find the source of the blood. Benign conditions such as hemorrhoids can also cause blood in the stools.
The rectum and the lower part of the colon is examined with a lighted tube (sigmoidoscope) to look for polyps (benign growths that may lead to cancer) which may be removed by the doctor.
Using a long flexible tube with a camera (colonoscope), the doctor is able to examine the interior of the intestines and colon. If polyps are found, they may be removed.
Double-Contrast Barium Enema
This involves filling the colon and rectum with a white liquid material (barium) that enhances x-ray pictures. This allows polyps and other abnormalities to be seen clearly.
Special x-ray equipment is used to produce pictures of the colon and rectum. These pictures are assembled into detailed images using a computer to show any abnormalities such as polyps and tumours.
Not all symptoms of colorectal cancer indicate the actual cancer. The doctor will check the patient’s personal and family history, as well as perform a physical examination to determine the cause of the symptom.
If abnormalities such as polyps are found, abnormal tissue can be removed for a biopsy during colonoscopy or sigmoidoscopy. A pathologist using a microscope can then check the tissue for cancer cells.
How is Colorectal Cancer Assessed?
If the biopsy shows that cancer is present, the doctor will carry out further tests to determine the stage of the cancer. The stage is based on factors such as whether the tumour has invaded nearby tissues, whether the cancer has spread and, if so, to which parts of the body.
The stages of colorectal cancer are:
- Stage 0: The cancer is found only in the innermost lining of the colon or rectum. This is also known as pre-cancer, as the cancer cells have yet to develop and spread.
- Stage I: The tumour has grown into the inner wall of the colon or rectum, but not through the wall.
- Stage II: The tumour has extended deeper into or through the wall of the colon or rectum. It may have invaded nearby tissue, but cancer cells have not spread to the lymph nodes.
- Stage III: The tumour has spread to nearby lymph nodes, but not to other parts of the body.
- Stage IV: The cancer has spread to other parts of the body, such as the liver or lungs.
- Recurrence: This is cancer that has been treated and has returned after a period of time. The disease may return in the colon or rectum, or in another part of the body. There is a chance that the recurring cancer is more aggressive than normal.
The tissues that contain the tumour, as well as nearby tissue or lymph nodes, can be removed through surgery. This can be done using minimally invasive laparoscopy or open surgery.
Chemotherapy uses anti-cancer drugs to shrink or destroy cancer cells. The drugs enter the bloodstream and can affect cancer cells all over the body.
Targeted Cancer Therapy
In cases where colorectal cancer has spread, patients may be given targeted therapy. These are drugs or other substances that interfere with specific molecules involved in tumour growth, blocking the spread of cancer.
Radiation therapy, also called radiotherapy, uses high-energy rays to destroy cancer cells in the affected area.