Colorectal cancer is a cancer that develops from the cells of the large intestine. The large intestine consists of the colon and rectum. The rectum comprises the last 15 cm of the large intestine and lies within the pelvis, which consists of the hip bones. This is a very small area and the distance between the cancer and the surrounding normal organs is very short. Hence, the chance of the cancer spreading to neighbouring organs in the pelvis is significantly high.
The colon forms the rest of the large intestine that lies above the level of the hips. It is surrounded by fatty tissue, called omentum, and anchored by more fatty tissue (called mesentery) to the walls of the abdominal cavity. The lymph glands are in the mesentery.
Cancer can develop from the cell-lining of the large intestine. The cancer can cause blockage of the intestine, or bleeding in the faeces.
How Common is Colorectal Cancer?
Colorectal cancer is now the most common cancer in Singapore affecting both males and females. There were about 9,807 cases diagnosed from 2011-2015 locally.
Age of Onset
Most persons diagnosed with colorectal cancer are older than 45 years of age. Younger persons, below 20 years of age, if diagnosed to have colorectal cancer, are likely to have the hereditary form of colorectal cancer such as familial adenomatous polyposis.
Common symptoms that persons have are a change in bowel habits, such as persistent diarrhoea or constipation or a change in the frequency of stools. Passing blood mixed with stools is also a suspicious sign which always requires prompt medical attention. Other symptoms include persistent ill-defined abdominal discomfort or pain. Occasionally, a mass is felt in the abdomen.
The simplest way to detect a rectal cancer is by insertion of the doctor's finger into the rectum, i.e. a rectal examination. This can be done in the outpatient clinic, takes less than 5 minutes and causes minimal discomfort. However, this detects cancers only in the last 5 to 8cm of the rectum.
For cancers that are more distantly located in the large intestine, sigmoidoscope or colonoscope examination can be performed. These fiber-optic flexible tubes are inserted up the rectum into the colon. Through these scopes, removal of a small piece of growth for testing is possible. Insertion of these scopes are performed with minimal anaesthesia in an outpatient clinic. Although uncomfortable, the procedure lasts less than 30 minutes.
Barium enema is an x-ray examination performed to examine the whole length of the large intestine. A dye is passed through a narrow tube into the rectum and allowed to coat the length of the intestine. Multiple x-ray films are taken on various portions of the large intestine and abnormal areas identified. The doctor may further proceed to do a colonoscopy or a sigmoidoscopy so that a biopsy of these suspicious areas can be done.
The mainstay of treatment is surgery. The cancer, its surrounding fat, and lymph glands are removed during surgery. The two ends of the cut section are joined together. If for some reason the colon cannot be joined, an artificial opening for the colon, called a colostomy, may be required. This opening allows waste to be removed from the body when the normal opening cannot be used or has to be removed. A colostomy may be temporary or permanent.
Depending on the stage of the cancer, chemotherapy may be required after surgery to improve a person's chance of cure from the cancer. Chemotherapy involves injections of anti-cancer drugs into a vein on the hand. Chemotherapy, which lasts from 6 to 12 months, usually causes mild mouth ulcers, mild diarrhoea, mild hair loss, possible darkening of complexion, and nausea. The most common medicine used is 5- fluorouracil, though other drugs may be also be used.
Treatment of Rectal Cancer Again, the mainstay of treatment is surgery. Due to the position of the rectum in the bony pelvis, the chance of cancer radiation therapy is sometimes used to reduce the size of the colorectal cancer before surgery. More often, it is used after surgery to destroy any remaining cancer cells and prevent the cancer from recurring. Radiotherapy involves giving high-energy rays into a small area where the original cancer was. The course of treatment, given daily for 5 minutes, usually lasts 5 to 6 weeks. Side effects which may occur include diarrhoea, tiredness, skin redness and rash. In some women, radiotherapy brings on early menopause. spreading to the surrounding organs, such as bladder, uterus and bone, is high. Even if the cancer was totally removed by surgery, there is concern that undetectable cancer cells may lie in the vicinity since the distance between cancer and normal tissue is so short. Hence, depending on how far the cancer has invaded the surrounding fat and organs, As with colon cancer, chemotherapy may also be required, after surgery. Radiotherapy may be given together with chemotherapy. Prognosis of Colorectal Cancer A prognosis is the probable outcome of an illness based upon all the relevant facts of the case. All findings from clinical examination and x-ray investigations and pathology reports are important and must be considered together to decide what the progress of an individual case of colorectal cancer may be. From this, the appropriate course of treatment can be decided and put into action. The treatment strategy will vary from person to person. With prompt and appropriate treatment, the outlook for a person with early colorectal cancer is good.
I have haemorrhoids. Will these become cancerous?
Haemorrhoids are enlarged blood vessels of the rectum. They
arise because of constipation or pregnancy. They do not become cancerous.
However, they will bleed from time to time and over the years may cause anaemia
or a lack of red blood cells which may cause symptoms such as tiredness and
breathlessness. Haemorrhoids that bleed, itch or discharge mucus should be
attended to by a medical professional. Any bleeding from the back passage
requires investigation and should not be assumed to be haemorrhoidal in origin.
My father/uncle was diagnosed to have large intestinal cancer.
Am I at higher risk of getting the cancer?
Persons considered to be at high risk of being diagnosed with
colorectal cancers are persons with a history of colorectal polyps, previous
colorectal cancer, persons with one immediate relative diagnosed to have
colorectal cancer before the age of 45 years old, persons with two or three
immediate relatives diagnosed with colorectal cancer at any age, and persons
with a family member known to have familial adenomatous polyposis.
Any patient with familial adenomatous polyposis is usually
informed by his surgeon to send the rest of his family for the screening. This
is a hereditary condition where hundreds and thousands of polyps develop in the
colon, rectum and occasionally stomach. It is usually present by the teenage
years. The risk of developing colorectal cancer from one of these polyps is
very high. Very often, the affected person has his colon removed before the
development of colon cancer. He or she can still lead a normal life after
surgery. The diagnosis of familial adenomatous polyposis is usually made on
sigmoidoscopy or colonoscopy. Recently, a blood test that can detect the
abnormal gene responsible for this condition has been developed.
Persons considered to be at high risk of developing colorectal
cancer should consider undergoing colonoscopy every 3 years. Persons with a
history of colonic polyp should consider colonoscopy and removal of polyps
every year until no new polyps develop. Thereafter, colonoscopy should be
performed every 3 years.
I am afraid of being diagnosed with colorectal cancer. Should I
go for screening?
If you are worried about colorectal cancer, you can discuss the
possibility of faecal immunochemical testing with the general practitioner. The
most effective screening test is colonoscopy, which is recommended in some
countries for routine screening of individuals aged 50 to 70 years old every 3
I have been diagnosed to have colorectal cancer. How long will I
Many people who have had colorectal cancer live a normal
lifespan. Current treatments offer a good prognosis, but you may require
several types of treatment to have the best chance of avoiding recurrence of
Useful websites that cover this topic:
Singapore Cancer Society www.singaporecancersociety.org.sg
American Cancer society: Colorectal Cancer Resource Centre www.cancer.org/docroot/LRN/LRN_0.asp?dt=10
Macmillan Cancer Support www.macmillan.org.uk/Home.aspx
Cleveland Clinic: Foundation: Centre for Colon Cancer and Polyps
Colon Cancer Alliance www.ccalliance.org
For further enquiries on colorectal cancer, please call the
Cancer Helpline at (65) 6225 5655 or email to email@example.com.
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