In Singapore, about 1,900 people are diagnosed with colorectal cancer every year. It is the most common form of cancer in men above the age of 50.
Seeing blood in your stools can be frightening. However, it does not always mean that you have colorectal cancer. There are many other tell-tale signs.
In this guide, I will cover topics about colorectal cancer that you should know about. They include:
- types of treatment methods,
- ways to diagnosis and
- ways to reduce your risk of getting colorectal cancer.
Read on to find out.
What is colorectal cancer?
Colorectal cancer is a cancer that is found in the large intestine or colon. The function of the colon is to:
- absorb water and electrolytes from waste products,
- produce and absorb certain vitamins,
- allow bacterial fermentation,
- storing of faeces
- and moving faeces towards the anus.
Colorectal cancer arises from the innermost layer of the 4-layered colonic wall. This is the layer that is in contact with stools and helps absorb nutrients from your stools .
How common is it?
Colorectal cancer is the most common cancer to affect Singaporeans. Among males, it is the:
- most common cancer for men above the age of 50 and
- 2nd most common for men below 50.
Meanwhile, for females, it is the:
- the 2nd most common overall and
- most common cancer post-menopause.
While many of these people can be cured, more than 50% are in the advanced stages. Thus, those in stages 3 and 4 have a poor chance of cure.
The risk of developing colorectal cancer rises with age. Around the world, the risk rises gently from the age of 20 but dramatically after 50.
In Singapore today, about 20% of colorectal cancer patients are below 50. 20 years ago, it was below 10%. Evidently, there is a rising trend of colorectal cancer occurring at younger ages.
How does it develop?
There are 4 layers in a normal colonic wall. The innermost layer is called the mucosa, where cancer cells can arise. Before it can become cancer, a normal colonic mucosal cell must undergo some changes. These changes happen in the genes of the cells and are called genetic mutations.
It takes 10-15 years for a normal cell to transform entirely into a cancerous cell. While we know some of the defects, we do not fully know what triggers them. Some of these abnormal genes can also be inherited. If one has an abnormal gene, the conversion process is faster.
The colonic mucosal cell grows larger as it changes, appearing as a lump called a polyp, and protrudes into the lumen of the colon. As defects develop, the polyp grows larger. Eventually, cancer develops within the polyp.
When the colorectal cancer gradually develops, it grows towards the outer layers of the colonic wall. It can then spread into the blood or lymphatic vessels. The lymphatic vessels drain into lymph nodes outside of the colonic wall. These lymph nodes help to trap cancer cells from spreading further. However, if the cancer cells enter the blood vessels, they can travel far and wide to other internal organs. This process is known as metastasis.
What are the signs?
In the polyp phase, or before cancer, there are usually no tell-tale signs. A colonic polyp is considered large when it is more than 1 cm in length. With that said, it may bleed as stools brush across its surface. This may be seen as small streaks of blood in the stools. Sometimes, the amount of blood is so little that our bare eyes cannot see it.
When one has developed colorectal cancer, the common symptoms are :
- change in bowel habit,
- blood in the stools,
- mucus in the stools or
- constant urge to pass stools.
It might be a sign of colorectal cancer if:
- your bowel habits have changed and
- persisted for more than 2 weeks.
Changes in bowel habits
Every one of us will experience some changes in our bowel habit patterns from time to time. In a normal case, these will resolve within 2 weeks. If a person develops cancer in the rectum, it can feel like a lump of stool is stuck inside the rectum. You will constantly feel like you need to pass stools but nothing comes out.
Some factors to look out for are:
- frequency of passing stools,
- size of the stool,
- colour of stools.
In the more advanced stage of colorectal cancer, you may feel a lump in your abdomen (such as when you shower). Moreover, you may develop persistent abdominal bloating or suffer pain before passing stools.
Blood in stools
If you see blood in your stools or when you wipe after passing stools, you should consult your doctor for further advice. Colorectal cancer is not the commonest cause of blood in stools. With that said, it is the most important diagnosis to exclude.
Mucus in stools
If you pass mucus in your stools, it appears like clear phlegm mixed with stools. Sometimes, you may think you have diarrhoea. Instead, the stool is not watery but is solid and mixed with mucus.
What happens when the cancer blocks your colon?
When that happens, you can develop abdominal distension, abdominal pain or vomiting. In rare cases, the cancer can burst through (perforate) your colon. As a result, it causes sudden and severe abdominal pain.
Furthermore, if the cancer has been present for a long time or has spread to other organs of your body, you may become pale from anaemia (low red blood cell count). Anaemia happens because the cancer bleeds continuously. You may also feel tired all the time. In addition, the cancer can secrete proteins which make you lose your appetite. Thus, you may lose weight as well.
If you know someone who looks pale or has lost a lot of weight without reason, you should encourage the person to seek medical attention soon.
Symptoms of possible colorectal cancer :
- changes in bowel habit for more than 2 weeks,
- blood in the stools,
- mucus in the stools,
- urges to pass stools,
- unexplained anaemia (pallor),
- persistent weight loss,
- loss of appetite,
- abdominal bloating or pain.
Ways to diagnose colorectal cancer
The most accurate test to confirm colorectal cancer is through a colonoscopy. It works by passing a flexible tube through the anus to see the entire colon with a magnified camera. If polyps are present, these can be cut away (excised) and removed before they become cancerous. With that, a tissue biopsy can be taken to help plan treatment if cancer is present.
To assess the colon and abdomen, a CT scan may be used. It is used in some cases where colonoscopy cannot be performed. CT scan is not as effective as colonoscopy because polyps cannot be removed. Furthermore, a biopsy cannot be taken from the suspected cancer.
Patients will need to undergo blood tests and radiologic scans. This process starts after the confirmation of the cancer. Scans such as CT or MRI are used to plan for treatment. Your doctor will advise you on the best options specific to your cancer. So, be sure to consult a doctor to get your symptoms diagnosed.
How to treat colorectal cancer?
Treatment options for colorectal cancer are based on the stage of the disease. There are 4 stages of colorectal cancer.
It is the cornerstone of treatment. You must consult a surgeon who specialises in colorectal surgery. A trained colorectal surgeon can perform the surgery in a precise manner. In essence, good quality surgery can greatly improve the cure rate for patients with colorectal cancer. Most patients are also suitable for laparoscopic (keyhole) surgery. As a result, the recovery period can be shortened and reduce complications.
More than 95% of the patients who undergo surgery can have a single-stage surgery where:
- the segment with cancer is excised and
- the two ends of the bowel joined back (anastomosed) immediately.
Fewer than 5% of patients need to wear a stoma bag. The majority of those with stomas can have the stoma reversed at a later surgery. Only about 1-2% of patients need to wear a stoma bag permanently.
|Stages:||Description:||Actions to be taken:|
|1||Cancer is confined to the inner layers of the colon wall.||Surgery to remove segment containing cancer.|
|2||Cancer cells reach the outer layer, have yet to spread elsewhere.||Surgery - only treatment unless there are unique features of your cancer that raises your risk of cancer recurrence.|
Chemotherapy may be required if there are high-risk features after surgery.
|3||These cells have spread to the lymph nodes. These lymph nodes are located outside the colon wall, adjacent to the blood vessel of the colon.||To maximise cure rate, a combination of chemotherapy, radiotherapy and surgery is often needed.|
|4||It has spread to other internal organs.||Palliative treatments - ease symptoms|
In stage 4, while the prognosis is grim for many patients, some patients respond well to initial treatment. To allow potential cure, cancer can be down-staged. However, down-staging is a complex topic and your cancer specialists will discuss this with you if needed.
Chemotherapy and Radiotherapy
There are times where I feel that patients may benefit from chemotherapy or radiotherapy. With that said, I will work with the medical and radiation oncologist specialising in colorectal cancer. There have been significant improvements in medical and radiation oncology over the past 20 years.
Many patients who undergo these treatments today have few side effects and complications are becoming rarer. The majority can perform normal activities during treatment, with no visible effects of treatment. Here are some common side effects:
- temporary numbness of the hands and feet during treatment,
- temporary darkening of the skin and
- abdominal bloating.
Meanwhile, here are some of the more uncommon side effects:
- hair loss,
- weight changes and
- blood clotting problems.
Lately, the newly developed drugs had gained more interest. It targets cancer cells uniquely. These “targeted therapy” drugs are not indicated in the majority of colorectal cancer patients. There are rare cases where the genetic profile of cancer shows that the drugs are suitable. With that said, in these cases, the medical oncologist will discuss this option. Whenever in doubt, consult your doctor to find out which treatments are more effective for you.
The cure rate of colorectal cancer
The overall cure rate for colorectal cancer is dependent on:
- your stage of the disease,
- quality of surgery and
- response to treatment.
|Stage:||Chance of cure after surgery in most patients:|
|1||more than 95%|
|2||more than 80%|
|3||more than 50%|
less than 10% for those who respond well to treatment
Chance of down-staging cancer: more than 30%.
Thus, the main point here is that early diagnosis leads to the best chance of cure.
What if I do not get my colorectal cancer treated?
Colorectal cancer, if left untreated, will continue to grow. The colon is essentially a tube to allow stools to pass to the anus. If the cancer encircles the circumference of the colon, it can obstruct the passage of stools, also known as intestinal obstruction. When that happens, your abdomen will bloat and the blocked intestine causes pain. When the blockage worsens, you may vomit.
The increasing swelling of the blockage can cause the colon to perforate. Perforation of the intestine without treatment of surgery will cause a patient’s death within a week.
In some cases, the cancer does not cause intestinal obstruction or perforation but spreads to other internal organs. The cancer cells cause appetite loss and drain you of energy. Thus, it leads to weight loss and the internal organs affected by cancer can deteriorate and fail. If internal organs like the liver or lungs fail, the outcome is catastrophic. If the cancer cells spread to your bones or nerves, it can cause persistent pain that can only be ameliorated by strong painkillers.
I want to let you know that in rare cases your doctor may advocate the option of not treating you aggressively. I consider this option if:
- the cancer advanced, thus making it incurable or
- if you suffer from significant medical conditions which increases your risk of death from treatment.
For example, an elderly patient with kidney failure requiring regular dialysis who also has stage 4 colorectal cancer.
Speak to your colorectal surgeon and talk about all your options. When you have doubts, you should seek a second opinion from another colorectal surgeon.
How can I reduce my risk of colorectal cancer?
Firstly, you need to understand the factors that affect your risk of colorectal cancer. Thus, this will allow you to know how to reduce the chances. There are risk factors you cannot change and those you can .
The factors are:
- A family history of colorectal cancer or polyps
- IBD, or also known as Inflammatory Bowel Disease
- Inherited cancer syndromes
While the risk of getting colorectal cancer increases with age, we are seeing more patients develop colorectal cancer before 50 years old. This pattern is similar around the world. The risk continues to increase when you grow older, even after the age of 80 years.
Family history of colorectal cancer or polyps
About 1 out of 5 colorectal cancer patients have a family member who has had colorectal cancer or polyps before.
Risk of colorectal cancer increases if one of your first-degree relatives has cancer or polyp. If there are 2 of them, your risk is doubled! First-degree relatives include your:
- siblings or
Inflammatory bowel disease
Patients suffering from inflammatory bowel disease (IBD) are at a higher risk. They will require regular colonoscopy surveillance. Likewise, it applies to those who have their disease well-controlled too. IBD includes Ulcerative Colitis and Crohn’s disease.
Inherited cancer syndromes
A handful of people who develop colorectal cancer have inherited gene defects (mutations) that cause the disease. Often, these defects lead to cancer that may occur at a young age. In Singapore, the percentage of colorectal cancer patients with inherited cancer syndromes is unclear.
About 5% of patients may have inherited cancer syndromes. Identifying families with these inherited syndromes is equally as important. We can suggest screenings and other preventive steps at a much earlier age.
A person’s ethnicity affects his/her risk of colorectal cancer. In Singapore, the risk is the highest among Chinese when compared to Malays and Indians. Indians have the lowest risk out of the three groups. Furthermore, a similar pattern can be seen in America. African Americans have a higher risk than Caucasians for colorectal cancer.
In short, all the factors mentioned in the past few sections cannot be changed. But, identifying them helps you determine when you should screen for possible colorectal cancer. Even if you do not have any symptoms yet, you should go for a screening.
While there isn’t anything that can be done for the unchangeable factors, there are a few factors that can be helped. To list, these factors are:
- Your diet
- Smoking habits
- Heavy alcohol consumption
- Obesity 
- Being physically inactive
A diet high in fibre can reduce your risk. In other words, your diet should include:
- vegetables and
- whole grains.
Conversely, a diet high in red meat and processed meat can increase your risk. Cooking food at high temperatures (such as grilling and barbecue) raises the risk as well.
Smoking & Alcohol Consumption
Likewise, smoking increases your risk of colorectal cancer about two-fold. The carcinogens from smoking are more well-known for the association with lung cancer. Not only that but it also increases the risk of many other types of cancers, including colorectal cancer. Consuming more than 2 alcoholic drinks a day increases the risk of colorectal cancer as well.
Obesity & Physical inactivity
Besides that, obesity is associated with an increased risk of colorectal cancer. It has the potential to increase your risk of complications when you undergo treatment. What is often under-reported is the potential benefits of an active lifestyle.
People who regularly engage in exercise at a moderate intensity have a 30-40% lower risk as compared to people who do not. Examples of such exercises are jogging and swimming three times a week for at least 30 minutes.
Exercise induces the body to repair your muscles. Thus, this process helps the body identify abnormal cells and repairs them too. Thereby, this reduces your risk of cancer. Besides, regular exercise helps reduce the risk of:
- prostate and
- breast cancer.
Therefore, my recommendation to reduce your risk is to:
- exercise regularly,
- stop smoking,
- eat more vegetables and fruits
- and reduce your red meat consumption .
To add on, these recommendations are very similar in ways to reduce the risk of hypertension and heart diseases.
How can I prevent or screen for colorectal cancer?
The dietary and lifestyle recommendations above can help you to reduce the risk of colorectal cancer. However, even if you adopt a healthy diet with good lifestyle habits, it does not mean that you are free from colorectal cancer. Ageing and inherited genes can also increase your risk of colorectal cancer. Therefore, you should consider colorectal cancer screening.
The Ministry of Health first published guidelines in screening for colorectal cancer in 2003. These guidelines have been revised in 2019. Age 50 is the recommended starting age for screening for all individuals . Whenever in doubt, you should always consult a doctor.
5 tests can be performed to screen for colorectal cancer. Namely, they are:
- Faecal occult blood test. Currently, Singapore uses the faecal immunochemical test, also known as FIT .
- Flexible sigmoidoscopy
- Flexible colonoscopy
- Barium enema
- CT colonography or also known as virtual colonoscopy
Today, the most widely performed test is FIT. This test can be performed at home and it is the cheapest screening test available. An instruction sheet will guide you on how to perform the test. The kit also has a double-sealed bag coupled with a self-addressed envelope to send the sample to the hospital.
The recommendation of colonoscopy is brought up if the FIT shows blood in your stools. FIT is cost-effective and can reduce the chance of death from colorectal cancer as it may diagnose cancer in its earlier stages. However, FIT does not help to prevent colorectal cancer .
Colonoscopy is the gold standard test to screen for colorectal cancer. It is the most accurate test and it allows your doctor to take a biopsy to confirm cancer. More importantly, colonoscopy can detect pre-cancerous polyps.
These polyps are usually silent. They don't come with any symptoms. Removal of polyps stops the chance of it becoming cancerous. Colonoscopy, with the removal of pre-cancerous polyps, is the only method to date to prevent colorectal cancer.
Flexible sigmoidoscopy is like a colonoscopy. The main difference is that only the left half of the colon is assessed. It has been superseded by colonoscopy.
A barium enema is a radiologic test. It involves barium, a white liquid which can be seen on the X-ray. In the beginning, it is pumped into the rectum followed by air. A series of X-rays are then taken to view the colon. During this process, you would be lying on a bed that can be tilted which allows the barium to flow all the way in through the colon. This method is not well-liked by radiologists and patients alike. Therefore, it is used only if all else fails.
CT colonography requires a person to have a CT scan done in the prone and supine position. A computer software then merges the two scans to create a 3D image of your colon. Due to the amount of radiation used, it is also used only if colonoscopy fails.
While all five tests are available, FIT and colonoscopy are the tests that are regularly performed. The table below summarises the screening guideline for healthy individuals. They also should have no prior colorectal polyps or family history of colorectal cancer or polyps. People with an increased risk of colorectal cancer will have a different set of guidelines. This is something that they should discuss with their doctor.
Age of onset for screening:
50 years old
50 years old
Every 10 years
50 years old
Every 5 years
50 years old
Every 5 years
50 years old
Every 5 years
Colorectal cancer is the most common type of cancer to affect Singaporeans. The process of colon cells transforming into polyps and then subsequently colorectal cancer is well described. The removal of precancerous polyps by colonoscopy can prevent colorectal cancer. However, this is the only known way to date to prevent this cancer.
A healthy diet and active lifestyle can help reduce your risk of developing colorectal cancer. Even with a good diet and lifestyle, everyone should go for colorectal cancer screenings when they have reached the age of 50 years.
If anyone has signs and symptoms of this cancer, they should seek medical care promptly. Therefore, by diagnosing the cancer in its early stages, colorectal cancer is highly curable.
You can beat the disease!
Dr Lim Jit Fong is a colorectal surgeon at Lim Jit Fong Colorectal Centre. He specialises in general surgery as well as colorectal surgery. Dr Lim offers services ranging from anal fissures to functional disorders such as bowel incontinence. Furthermore, he holds several appointments. One of which is the President of the Society for Continence in Singapore.
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