In Singapore, colorectal cancer is the second most common cancer in men and the 2nd most common cancer in women. Combined it would be the most common cancer.
In Singapore, the risk of a person getting colorectal cancer during his or her lifetime is 5.6%, about 1 in 20. There are about 1500 new colorectal cancers cases diagnosed every year. If diagnosed early, there is chance for cure.
Rectal cancers account for around 30% of the total number of colorectal cancers seen here.
What is colorectal cancer?
It is cancer arising from the colon or rectum. Usually it arises from the epithelium (inner lining) of the gut wall.
Who can get colorectal cancer?
Colorectal cancer can affect any age, any race and both sexes. It is more common after the age of 50 years, more common among the Chinese. For colon cancer, the incidence is the same between males and females, whereas rectal cancer is more common among males.
How do we know we have colorectal cancer?
These are the warning symptoms that would alert us to look out for colorectal cancer.
- Blood in the stools
- Change in bowel habits
- Unexplained Anaemia
- Unexplained abdominal pain
- Abdominal mass
But bear in mind that especially in the early stages, colorectal cancer can be a silent disease and not have any symptoms at all.
How do you make the diagnosis?
Usually the doctor will be suspicious if you have some of the warning symptoms or if he feels a mass in your belly or rectum during examination. Oftentimes the diagnosis is confirmed during the colonoscopy(when the tumour is visualized) and when a biopsy will be taken. Sometimes the diagnosis can be made on barium enema, CT colonography or CT scan findings as well.
What is the cause of colorectal cancer?
No one really knows. But it is a combination of genetic causes and environmental causes. About 15% of colorectal cancers have a strong genetic basis. There have been certain well-defined genetic syndromes, namely, the Familial Adenomatous Polyposis (FAP) and Hereditary Non-Polyposis Colorectal Cancer (HNPCC).
Dietary causes account for about 90% of environmental causes. There is some link between colorectal cancer and certain factors, ie obesity, high caloric intake, alcohol intake and tobacco smoking, just to name a few.
What can I do to prevent colorectal cancer?
The best known way to decrease the likelihood of colorectal cancer at this point in time is colorectal screening. There is no guaranteed formula to prevent colorectal cancer. But certain general measures can be helpful. Like exercise, taking fibre, having moderate caloric intake, eating lean meat and fish, moderate carbohydrate intake and reducing refined sugars and starches. There is no evidence that ‘antioxidants’, colonic irrigation or herbal remedies help lower the risk of colorectal cancer.
What is special about rectal cancer?
The special thing about the rectum is that it is located within the pelvis, which is a limited space, about the volume of a jam jar. For men, the rectum, the bladder and the prostate are all within that area and for women, the rectum, uterus and bladder. This plays a role because of the limited space; it is easy for the cancer to grow from the rectum into the prostate or bladder, or for women, the uterus and bladder.
The rectum is near anus (the end of the gastrointestinal tract). The anal muscles are the structures responsible for faecal continence, that is, it is closed when a person is moving around so that stool doesn’t leak out and it is also able to relax and open to let stool out during a bowel movement. For the rectal cancers which are very close to the anal sphincter (anal muscles), there is a possibility that cancer cells have invaded the anal sphincter and have to be removed as well. The implication of that is after surgery, the patient would have to ‘wear a bag’ and have his bowel movements through an ostomy. Not all rectal tumours would need that; it is only those which are very close to the anal sphincter.