Colorectal Cancer is the most common cancer in Singapore 

Colorectal cancer is a cancer that arises in the large intestine or rectum. It is the most common cancer among men and second most common cancer among women.

Colorectal cancer can be prevented or effectively treated if diagnosed early. Some of the common symptoms include a change in bowel habits, blood in the stools or persistent abdominal pain.

Besides symptoms, what are the possible causes and risk factors? Is regular screening recommended? What are the types of treatments available for colorectal cancer?

Specialists from the Division of Radiation Oncology at National Cancer Centre Singapore (NCCS), a member of the SingHealth group, are here to answer your questions on Colorectal Cancer.

This As​k The Specialist forum has closed. Thank you for your interest and participation.

1. Question by g*******
I believe Colonoscopy is the most effective way to detect and prevent colon cancer. Besides this, is there any other way to detect it? What is the percetage of people using these methods and their effectiveness? Thanks.

Answered by the Division of Radiation Oncology at National Cancer Centre Singapore (NCCS):
There are various screening methods for colorectal cancer, and each has its own advantages and disadvantages, and are used in different settings.

Stool-based tests such as the Faecal immunological stool test (FIT) or faecal occult blood test (FOBT) works by detecting blood in the stool. Singapore citizens and permanent residents aged 50 years old and above can obtain free FIT kits from the Singapore Cancer Society and selected pharmacies in Singapore. It is also available from CHAS GP clinics. This test is useful as an initial preliminary screening test, and can be done annually. If the test results are positive, a colonoscopy may be recommended to investigate for the cause. It is important to note that a positive stool test result does not necessarily mean that one has colorectal cancer. Other reasons for a positive result include bleeding piles and menstruation.

Colonoscopy is considered the ‘gold standard’ test for colorectal cancer screening as it allows better detection of cancers and pre-cancerous lesions. If a tumour is seen during the procedure, a sample can be taken to confirm if it is cancerous. If polyps are seen, they can also be removed in the same setting to test for cancer, as well as to prevent them from potentially becoming cancerous in future. If the colonoscopy is normal, it can usually be repeated again every 10 years.

A scan called a CT Colonography can also be done to detect growths in the colon. The advantage of this is that it is not invasive, but the disadvantage is that a colonoscopy would still be required to investigate and biopsy any abnormal growths to confirm the diagnosis. There is also some radiation exposure each time a scan is performed.

2. Question by A*************
My father has Stage 4 Colorectal cancer and he has been combating it for many years. Despite repeated rounds of standard and targeted chemotherapy, metastasis still occured and it is now affecting his spine and kidneys too. Are there any possible treatments to help alleviate his pain?

Also, I have read that colorectal cancer can be hereditary, may i ask what would then be the recommended age for me to start checking for colorectal cancer and what kind of tests should I be doing (like colonoscopy, etc). 
Thank you so much

Answered by the Division of Radiation Oncology at National Cancer Centre Singapore (NCCS):
Dear reader, thank you for sharing your father’s battle with stage 4 colorectal cancer. Indeed, pain can be a difficult symptom to manage in patients where the cancer has spread to different parts of the body. Depending on the exact cause and mechanism of the pain, there are various options available. In general, pain can be reduced using appropriate pain medications at the appropriate doses and timing. Some patients may also require a combination of medications to bring their pain under control. 

Apart from medication, other treatments may also be helpful depending on the exact cause of the pain. This could include non-invasive treatments such as radiation therapy to the painful tumour, or minimally invasive procedures such as a nerve block injection or injection of cement to treat fractures in the bone of the spine. It would be helpful to have a discussion with your father’s oncologist to see if these are appropriate for your father’s condition.

Approximately 5-10% of colorectal cancers are hereditary. Hence in certain patients, screening for colorectal cancer may be recommended to start earlier than at 50 years old, depending on the risk assessment. This takes into consideration different factors, such as whether you have one or more first-degree relatives who developed colorectal cancer, how old they were when they were diagnosed, and whether you have a personal history of polyps or other cancers. It would be important to discuss this with your physician as individuals with an increased risk of colorectal cancer should have a personalized screening strategy. The recommended method for screening in your case would be a colonoscopy, and the exact age to start screening would depend on the age at which your father was diagnosed.

3. Question by Anonymous 
My parents are in their 50s with no known digestive problems. Should they go for fecal occult blood test annually or colonoscopy as general cancer screening?

Answered by the Division of Radiation Oncology at National Cancer Centre Singapore (NCCS):
FOBT or FIT is a useful preliminary screening test in individuals like your parents who are above 50 and without any symptoms, provided that they do not have risk factors, such as a family history of colorectal cancer or personal history of polyps or previous colorectal cancer. These test kits are readily available, easy to do, non-invasive, and can be done annually.

Colonoscopy is the ‘gold standard’ test used for screening as it is more accurate and allows detection and removal of pre-cancerous polyps. It is also the recommended screening method for individuals at a higher risk of colorectal cancer, such as those who have a positive family history. For individuals with no risk factors for colorectal cancer and have a normal colonoscopy, the test can be done again in 10 years.

4. Question by s*******
Dear Doctor,
I heard from friend that certain race (e.g. Chinese and Japanese) that has soya sauce in their diet/cuisine has higher chance in sufferring from colorectal cancer in life. Is this true ?
(I am Chinese, 40s, male)
thank you,

Answered by the Division of Radiation Oncology at National Cancer Centre Singapore (NCCS):
Dear reader, thank you for your question. An excessive consumption of certain foods such as red meat and processed meats has been linked with a higher risk of developing colorectal cancer. On the other hand, certain foods such as vegetables, fruits and grains have been linked to a reduced risk of developing colorectal cancer. However, there is no conclusive evidence that soya sauce increases the risk of colorectal cancer.

5. Question by y*********
I am a 25yo female and has been experiencing very irregular bowels since I was young. On average, I only release my bowels once every 2-3 weeks, sometimes even requiring the help of laxatives. This is despite proper diets of fruits and vegetables and intake of water. But to add on, I do cut down on my intake of food for fear that all the undigested food will be stuck inside. Would like to ask if this is potentially a symptom/risk factor of colorectal cancer. I do get abdominal pain occasionally, which I assumed is due to the buildup of stools. However, I did not have any experiences with blood in stools.

Answered by the Division of Radiation Oncology at National Cancer Centre Singapore (NCCS):
Thank you for your question. In general, it is uncommon for a person of your age to develop colorectal cancer unless you have a strong family history of colorectal cancer, or have underlying inflammatory bowel disease. As it sounds like your symptoms have been present for many years, it makes it less likely to be due to colorectal cancer since the symptoms would have worsened over time. I would suggest seeing a doctor for a formal assessment and evaluation of your chronic constipation as there could be other non-cancerous reasons for your symptoms.

6. Question by a****
1) Is colorectal cancer a painful cancer to die from if the patient chooses not to seek treatment?
2) What is the chance (percentage) of recurrence after treatment?
3) How long is a typical treatment when it has not spread?
4) How long does it take for the cancer to move from one stage to another if the person is not aware of having it?
5) Is this cancer caused by a virus or the body's own cell mutations?

Answered by the Division of Radiation Oncology at National Cancer Centre Singapore (NCCS):
Dear a****, thank you for your questions. The symptoms a patient experiences when cancer progresses varies from person to person. In general, when a colorectal cancer grows in size, it can cause symptoms such as abdominal pain, blockage of bowel and bleeding in the stools. It may also spread to other parts of the body and cause other symptoms depending on where it spreads to. 

If a patient is not suitable for, or chooses not to undergo curative treatment, there are also various palliative and supportive care options that can help to reduce symptoms. These may include medications to reduce pain, surgery to relieve bowel obstruction, radiotherapy to reduce bleeding and pain etc. Hence, even if a patient chooses not to undergo cancer treatment, there are supportive care options that can help to reduce their symptoms.

The chance of recurrence depends on the stage at which the cancer is detected. Hence the importance of screening, and also seeing a doctor early if have symptoms such as change in bowel habits, blood in your stools, thinner stools, feeling of incomplete passing of stools, unexplained weight loss etc. 

In general, the earlier a cancer is detected, the better the chances of survival. The 5 year survival rate of a stage 1 cancer can be above 80%, while a stage 4 cancer would be below 10%. However it is important to know that survival rates also depend on many other factors, such as the patient’s age, presence of other co-existing medical conditions, and the molecular characteristics of the cancer.

The duration of treatment depends on the stage of the cancer. Early stage cancer may only require surgery. More advanced rectal cancers may require a course of radiotherapy either before or after surgery, and it can range from 1 to 5.5 weeks in duration. Chemotherapy may also be required if the cancer is found to be advanced, and is usually given after surgery. The duration of chemotherapy is usually around 3 to 6 months.

The time it takes to progress from one stage to another also varies from person to person, and it is not possible to predict when or how quickly it will progress.

The majority of colorectal cancers develop from polyps in the bowel that become cancerous over time as mutations arise in their DNA. Colorectal cancer has not been found to be caused by a virus.

7. Question by J***
Is colorectal cancer hereditary? 
Please expound on what kind of change in bowel should we observe? 
Is there any food to avoid to prevent this from happening? 
Thank you.

Answered by the Division of Radiation Oncology at National Cancer Centre Singapore (NCCS):
Dear J***, thank you for your questions. The majority of colorectal cancer cases are non-hereditary. Only about 5-10% of cases are hereditary.

Change in bowel habits include symptoms such as diarrhoea or constipation, blood in the stools, stools that are thinner or narrower than usual, and a sensation that the bowel does not empty completely.

There are some dietary and lifestyle modifications that may reduce your risk of developing colorectal cancer. In terms of diet, a regular intake of vegetables, fruits and whole grains has been found to be linked to a reduction in colorectal cancer risk. It would also be helpful to reduce your intake of red meats and processed meats as they have been linked to a higher risk of colorectal cancer. Smoking, heavy alcohol consumption and obesity are other modifiable risk factors that can be reduced to lower your risk of colorectal cancer.

8. Question by S******
How often should colonoscopy be performed?
I have heard some doctors in Singapore say that colonoscopy should be routinely performed on an annual basis!

Answered by the Division of Radiation Oncology at National Cancer Centre Singapore (NCCS):
The time interval between colonoscopies depends on the situation.
If a screening colonoscopy is entirely normal, then a repeat scope is usually recommended in 10 years. However, there may be situations where closer surveillance is required. For example, if the patient has more than one first degree relative with colorectal cancer, or the first degree relative was diagnosed with colorectal cancer at 60 years or younger, then the scope may need to be repeated in 5 years. Or if the patient has a known hereditary condition that predisposes him/her to colorectal cancer, then the scope may need to be repeated every 1-2 years. The colonoscopy may also need to be repeated at closer intervals if polyps were found. It is important to have this discussion with your doctor as the frequency of the colonoscopy depends on their individual risk assessment.

Ref: L20