All you need to know about colorectal cancer

Colorectal cancer starts in the colon or rectum and is the most common cancer in developed countries today. PHOTO: PARKWAY CANCER CENTRE
Colorectal cancer starts in the colon or rectum and is the most common cancer in developed countries today. PHOTO: PARKWAY CANCER CENTRE

Dr Patricia Kho, a medical oncologist at Parkway Cancer Centre, provides some useful information about colorectal cancer, possible preventive measures and the medical advancements available.

What is it?

Colorectal cancer starts in the large intestine (colon) or the rectum (end of the colon). It is the most common cancer in developed countries today. People living in these countries have three times the risk of developing this.

In Singapore alone, 9,324 diagnosed colorectal cancer cases were reported between 2010 to 2014 with both men and women equally at risk. It is now the most common cancer among men and the second most common cancer among women in Singapore. Although it can occur at any age, it is mostly diagnosed in those over 50 years old. If detected early, it can be prevented or effectively treated.

Ninety per cent of colorectal cancer cases almost always starts with a polyp. However, it can take five to ten years for normal cells in the lining of the colon or rectum to mutate and undergo “methylation abnormalities”. This is when the cells change and grow without control. If a gene mutates over time, a non-malignant polyp may turn cancerous.

Beware of inherited risk

About five to ten per cent of all colorectal cancers may be hereditary.

The two most common inherited colorectal cancer syndromes are hereditary non-polyposis colorectal cancer (HNPCC) and familial adenomatous polyposis (FAP). HNPCC cases account for three to five per cent of the population while FAP cases happen to less than one per cent.

Polyps can be removed from the colon. PHOTO: iSTOCK

People who carry the same cancer syndromes as their family members carry a higher risk and the cancer may develop before age 50. For example, those with HNPCC often have at least three family members and two generations with colorectal cancer while FAP patients can have hundreds of polyps in their early teenage life which may not become cancerous.

Inflammatory bowel disease (Crohn’s disease or ulcerative colitis) also increases one’s risk of colorectal cancer. The risk is higher if inflammation affects the entire colon.

Look on the bright side

From 2005 to 2014, the survival rate for both males and females has increased from 45 per cent to 50 per cent across all ethnic groups.

Medical advancements, particularly in the field of personalised medicine, have increased the chances of survival. Plus, genomic profiling helps to tailor treatment according to the cancer characteristics and genetic make-up of the individual.

New drugs such as Cetuximab and Panitumumab, which cleverly block colorectal cancer cells from further growth, have been found to work well for advanced-stage patients who carry the non-mutated (wild-type) KRAS and N-RAS gene.

A form of cancer treatment, immunotherapy which marshals the body’s own immune defences against cancer, also offer hope to some colon cancer patients.

Cultivate the good

It helps to exercise self-control in your lifestyle and eating habits.

Stop smoking: Each puff of a cigarette contains more than 60 cancer-causing carcinogens.

Limit alcohol intake: Alcohol can act as an irritant. Damaged cells may try to repair themselves, which could lead to DNA changes in the cells. In the colon and rectum, bacteria can convert alcohol into large amounts of acetaldehyde, a chemical that has been shown to cause cancer in lab animals. Men should limit their intake to two alcoholic drinks and women to one alcoholic drink a day.

Exercise regularly: One hypothesis is that high levels of insulin or insulin-related growth factors in obese people may promote colon cancer development. Maintain a lower end of body mass index (BMI) to reduce the risk of getting colorectal cancer.

Watch the diet: Avoid excessive consumption of food consisting of red and processed meats with presence of animal fats like those found in ham, bacon, sausages and local delicacies, bak kwa are some examples. It is recommended that you limit your intake to 500 gram of cooked meat per week with large portions of fresh greens and fruits per meal.

Based on HPB's guidelines, a colonoscopy should be done every five to 10 years. PHOTO: PARKWAY CANCER CENTRE

Go for a colonoscopy

Many people are still unaware of how a colonoscopy can help in preventing colorectal cancer.

Because it takes five to 10 years for a polyp to become cancerous, a colonoscopy — a relatively painless and fuss-free procedure — can make a big difference. Based on Health Promotion Board's (HPB) guidelines, colonoscopy should be done once every 10 years if the results from the first colonoscopy show no abnormalities and there is no increased risk of colorectal cancer.

High-risk individuals with family members who have had colorectal cancer should go for a colonoscopy earlier after discussion with the relevant medical professionals.