COLON cancer is the commonest form of cancer in men, and the second commonest in women (after breast cancer).
This is why it’s important to look out for early warning signs of this disease and then go for a medical check up early, says gastroenterologist Dr Maylene Kok.
This cancer involves the lower digestive tract or large intestine (colon and rectum). Every year in Malaysia, 15 in 100,000 men and 11 in 100,000 women are diagnosed with this disease. This makes it the second commonest type of cancer (after breast cancer) according to the Malaysian National Cancer Registry.
“Chinese men and women have a higher incidence of it, followed by Malays and then Indians,” says Dr Kok who is a consultant gastroenterologist at Subang Jaya Medical Centre (SJMC) in Selangor.
“People with certain underlying genetic predispositions, as well as those with inflammatory bowel disease, are also at higher risk compared to the general population.”
So what are the symptoms people should look out for?
Unfortunately, in the early stages of colon cancer, there are usually no obvious warning signs.
But as the tumour grows, one may start developing symptoms, but these vary, depending on the location and the size of the tumour.
Common symptoms to look out for are unexplained weight loss and a change in the bowel habit, including diarrhoea and constipation, says Dr Kok.
It also pays to look into the toilet bowl after a bowel movement to view the character or consistency of your stools.
Dark or black stools may imply digested blood from internal bleeding of the bowel. If you pass out fresh red blood during defecation, it may mean piles or haemorrhoids. But it could also be a sign of colon cancer.
Due to loss of blood in the colon, some patients may also have symptoms of anaemia, such as breathlessness, a feeling of near-fainting or light-headedness, palpitations, or in severe cases, chest pain.
Screening for people without symptoms is recommended from the age of 45 years onwards. If certain risk factors are present (for example, inflammatory bowel disease), then it is advisable to do screening at a younger age.
Health screening blood test packages often include cancer or tumour markers. For colon cancer, the most common tumour marker is carcinoembryonic antigen (CEA).
A high CEA may indicate that you have colon cancer, but it’s not conclusive, Dr Kok says. It may miss out on detection as colon cancer may not always produce an abnormal CEA. Or it may give a positive result unrelated to the colon. So CEA should not be used alone as a screening test.
The more accurate screening tests for colon cancer are:
> Testing your stools, for example by faecal immunochemical tests (FIT), faecal occult blood tests (FOBT), or stool DNA tests.
> Examining the colon. This is done physically via a colonoscopy or virtually with a CT (computed tomography) colonography.
In a colonoscopy, a fibre-optic camera called a colonoscope is inserted into the anus and pushed in carefully to examine the entire large intestine.
“Although it is invasive, it is very safe and done under anaesthesia for the patient’s comfort and safety. It takes about 20 minutes or more to complete the procedure,” explains Dr Kok.
Crucially, a colonoscopy may be lifesaving because it allows early detection of pre-cancerous colonic growths or polyps, which can be removed on the spot. A full bowel preparation, using a laxative to clear the stools, is required prior to the procedure.
For those who are not able or willing to go through an invasive colonoscopy, an alternative is a colonography which uses CT scans to check the large intestine. This is also called a “virtual colonoscopy”.
“However, this CT scan may miss small polyps, and you will be exposed to a small amount of radiation during the scanning. If any abnormality is found, your doctor will discuss having a colonoscopy to address the situation,” says Dr Kok.
As the colon is part of the digestive system, diet and nutrition play central roles. A low-fibre, high-fat diet raises risks of colon cancer.
In 2015, the International Agency for Research on Cancer (IARC) classified processed meat (such as sausages, ham and bacon) as a definite cause of colon cancer (a Group 1 carcinogen).
Red meat (including beef, lamb, and pork) is slightly less dangerous and is classified as a Group 2A carcinogen while white meat (chicken and turkey) and fish do not seem to be associated with colon cancer, explains Dr Kok.
Other risk factors are lack of physical exercise, alcohol consumption, cigarette smoking and obesity.
As this is the month of Ramadan, it is worth noting that caloric restriction has been shown to have good anti-cancer properties. There are different types of fasting out there, from the popular intermittent fasting to prolonged fasting (lasting more than 24 hours).
Several trials have shown favourable effects with intermittent fasting in reducing cancer risks, but larger trials are needed to confirm these findings, says Dr Kok.
So how can people best deal with colon cancer?
“Be aware of the risk factors, as well as symptoms and signs of the disease. Get yourself screened if you are at risk. Prevention is better than cure,” advises Dr Kok.