Colorectal Cancer In Singapore
Where is the
Colon and Rectum?
The colon and rectum together form the large intestine. It is the last part of the digestive system. It begins where
the small intestine ends at the right lower corner of the abdomen. It travels upwards towards the liver at the right
upper quadrant, then turns and goes across the abdomen to the left upper quadrant. From there, it turns downwards
and travels to the left lower part of the abdomen.
It then travels towards the centre of the pelvis and goes straight down and ends at the anus. The rectum forms the
last 15cm of the large intestines and lies within the pelvis. It is so named because it is relatively straight.
What is Cancer?
Cancer is an abnormal growth of cells that has the ability to invade into surrounding organs as well as spread to distant sites.
How does Colorectal Cancer Form?
Colorectal cancer originates from the inner lining or mucosa of the colon and rectum. The lining of the colon is
continuously growing and shedding. As such, the lining or mucosa is undergoing cell replication all the times. With each
replication, there is always a chance of a mutation. Although most mutations are recognised as an error by the body and
the mutant cell is removed, sometimes these mutant cells escape the body's defence mechanism and continue to grow. As
they grow, more mutation may occur and after a sequence of 4 or 5 mutations in the cell, they may turn cancerous.
Most of the colon cancer follows the adenoma-carcinoma sequence. What this means is that the colon wall first mutates
into adenoma (a non-cancerous form) and over time with more mutation, changes into carcinoma (cancer).
The adenoma is usually in the form of a polyp which is a fleshy protuberance from the colon wall.
Larger polyps may appear to have a stalk due to the weight of
the polyp pulling on the colon lining.
With time, the adenoma type tissue in the polyp will turn cancerous. It then invades back into the polyp and up the
stalk (if there is one) and eventually into the wall of the colon.
Once colon cancer has invaded into the wall, it can then spread to distant organs either via the blood stream or the
lymphatic system.
To know more about colorectal cancer, contact Ho Kok Sun Colorectal today at 6737 2778. You can also schedule an appointment with our colon surgeon, Dr
Ho Kok Sun, for enquiries regarding our colorectal cancer screening options.
What Are the Different Stages of Colorectal Cancer?
Staging is a way to measure the spread of a cancer. The later the stage, the greater the risk of recurrence of the
cancer. This gives your doctor a way to predict your risks and to advise if further treatment is required.
Most treatments are based on the TNM system. T is for tumour, and it is giving a number of 1 to 4 depending on the depth
of invasion of the tumour at the wall of the colon or rectum. N is nodal status and is given based on the number of
affected lymph nodes around the region. N0 is given when none of the surrounding lymph nodes are affected.
The greater the number of affected nodes, the larger the N number (0,1 or 2). M stands for metastasis. This means that
the cancer has spread to distant organs. M0 means no metastasis and M1 means it has spread. M1 almost always equates to
a stage 4 cancer. Various combinations of the T, N and M stage will give the actual stage of the disease.
| AJCC Stage | TNM stage | TNM stage criteria for colorectal cancer |
| Stage I | T1 N0 M0 | T1: Tumor invades submucosa |
| Stage I | T2 N0 M0 | T2: Tumor invades muscularis propria |
| Stage II-A | T3 N0 M0 | T3: Tumor invades subserosa or beyond (without other organs involved) |
| Stage II-B | T4 N0 M0 | T4: Tumor invades adjacent organs or perforates the visceral peritoneum |
| Stage III-A | T1-2 N1 M0 | N1: Metastasis to 1 to 3 regional lymph nodes. T1 or T2. |
| Stage III-B | T3-4 N1 M0 | N1: Metastasis to 1 to 3 regional lymph nodes. T3 or T4. |
| Stage III-C | any T, N2 M0 | N2: Metastasis to 4 or more regional lymph nodes. Any T. |
| Stage IV | any T, any N, M1 | M1: Distant metastases present . Any T , any N. |
Cancer staging is accurate only after removal of the cancer. It is not possible to tell the stage of a cancer at the
time of colonoscopy. This is because a colonoscopy only allows
your doctor to see the inside of your colon and will not be able to see the lymph nodes nor other organs such as the
liver or lung.
CT scans will be able to tell if there is or is not metastasis (the M stage). It is not sensitive enough to tell the
status of the lymph nodes. Hence, if there is no spread to the liver or lung in the scan, the only conclusion that can
be drawn is that it is not a stage 4 cancer.
What Are the Signs and Symptoms of Colorectal Cancer?
It is important to note that polyps, even large ones, and early cancer may not have any symptoms at all. Symptoms also
depend on the site of the cancer and how far away it is from the end of the colon. When stools enter the colon from the
small intestines, it is in a semi-solid state. As it stays and travels along the colon, the water in it gets absorbed by
the colon and it becomes more solid.
As such, tumour in the right side of the colon do not usually cause much symptoms as the semi-solid stools can flow past
most tumours quite easily. The cancer may bleed silently as it is mixed in the stools and cannot be seen with the naked
eye. Patients with tumours here usually present late with symptoms of anemia (low blood levels). Symptoms of anemia
include tiredness, feeling breathless when walking the same distance or climbing stairs, frequent giddiness.
At the left side of the colon, the stools are more solid. Therefore, any narrowing of the colon lumen results in the
following disturbance of the bowel habit:
- The stools might seem to be narrower in size.
- Patients might also feel constipated as it is more difficult for the stools to squeeze through a narrower passageway. This might also alternate with diarrhea or loose stools as this type of stools can pass through the narrowed passageway more easily.
- Patients might also notice blood coating the stools. As a general guide, the blood seen is usually dark red in colour.
For tumours in the rectum, the patient may have the sensation of incomplete passage of stools. This is because the
presence of the tumour there imitates the presence of stools.
Other less specific symptoms include feeling of bloating and mucus in the stools. Pain is usually not a feature of colon and rectum cancer until it is at an advanced stage. One complication of
the tumour is intestinal obstruction. This means that the entire
passageway is blocked and the stools (and even flatus) are not able to pass through. This results in abdominal pain,
distension and at a later stage, vomiting. Intestinal obstruction is an emergency medical condition.
Physical examination usually does not yield much signs unless the cancer is in an advanced stage. A hard mass in the
abdomen is usually a sign of a large tumour. An enlarged liver signifies spread of the cancer to the liver. In some
rectal cancers, a digital rectal examination where your colorectal doctor inserts a finger up the anus may pick up
earlier cancers. As such, if your colorectal doctor thinks that you warrant a rectal examination, please
do not decline or refuse for fear of discomfort or embarrassment.
What are the Risk Factors of Colorectal Cancer?
Genetics
Age
Family History
When there is a first degree relative (parents, siblings or children) with colorectal cancer, the risks increase 3 times to about 6%. If this relative is below the age of 50 at the time of diagnosis, the risk goes up to about 10%. If there are 2 first degree relative (for example, father and brother) with colorectal cancer, the risk is 17%. With 3 first degree relative, the risk is almost 50%.
Personal History of Colonic Polyps and Colon Cancer
Personal History of Inflammatory Bowel Disease
How Do You Screen for Colon Cancer in Singapore?
All the different tests to examine the colon requires proper cleansing of the colon. There are 3 different ways to examine the colon: colonoscopy, barium enema and computer tomography (CT) colonography (also known as virtual colonoscopy).
Colonoscopy
Colonoscopy is usually done under sedation though some patients opt to be awake and watch the entire proceeding. The major advantage of colonoscopy is that it is not just a diagnostic procedure, but it also allows for removal of polyps and to take tissue samples for testing.
Most people are fearful of colonoscopy because they feel that it is a very invasive procedure and are concerned about pain. Most patients do not feel any pain or even remember about the procedure after the they wake up from sedation. The most feared complication that may occur is that of perforation where the scope results in damage and a break in the colon wall. If that happens, colorectal surgery is usually required to rectify it. The risk is usually less than 0.1%.
Barium Enema
There is no sedation given for barium enema.
CT Colonography (also known as Virtual Colonoscopy)
| Colonoscopy | Barium enema | CT colonography | |
| Advantages | Accuracy- highest, especially for smaller polyps | Lower perforation risk | Lower perforation risk |
| Disadvantages | Perceived invasive test Perforation risk 0.1% | Least accurate No biopsy Perforation risk 0.04% | Accuracy in between barium enema and colonoscopy. Detection for polyps drop when size below 10mm Perforation risk 0.05 % |
| Sedation | Available | Not available | Not available |
| Intervention | Allows biopsy and removal of polyp | No | No |
CEA (Carcino-Embryonic Antigen)
On the other hand, people with an abnormally high level of CEA does not mean that they definitely have colon or rectal cancer. It just means that they need further investigations. A high level of CEA could arise due to both cancerous conditions (cancer of colon, rectum, stomach, lung etc) and non-cancerous conditions such as smoking, lung infection, colon infection etc.
Stool occult blood test
This test involves taking small sample to stools and sending it fresh (preferably within 48 hours).
The test is based on the assumption that if there any large polyps or cancer, it would bleed as the stools passes next to it. As this blood would have been mixed into the stools when it is passed out, it can no longer be seen with the naked eye. The accuracy depends on the different type of tests used to analyse the stools for blood and is in the region of 70-85%. Some of the older test requires abstinence from meat and other food for up to 3 days before the test and is very inconvenient. Unnecessary in delay or wrong storage of the stool sample prior to storage will also decrease the accuracy. What this means is that up to 30% of patients with colon and rectum cancer will have a negative result and be missed.
This test is more suited for population screening as it is cheaper and more convenient. This is not a diagnostic test for colon cancer. It is not for someone who already sees blood in the stools. It is just a warning indicator to go for a more complete examination of the colon.
What are the Treatments for Colon or Colorectal Cancer?
Surgery is the only treatment that a colorectal surgeon can offer for the definite cure of colon and
rectum cancer. Other treatment modalities such as chemotherapy and radiation therapy may be used as additional
treatment in reducing the risk of recurrence but do not consistently offer a cure.
The principle behind surgery for colon and rectum cancer is to remove the segment of colon or rectum with the
cancer together with the adjacent area containing the lymph nodes where the cancer would initially spread. After
the segment of the colon or rectum with the cancer is removed, the intestines are joined back to restore
continuity so that the patient can continue to pass motion in the normal manner.
In cases where the tumour is very close to or invading the anus, the anus would have to be removed to ensure
that the cancer is completely excised.
In certain cases of rectal cancer, the colorectal surgeon may also decide to pull out a temporary stoma. This is
because the joint (anastomosis) for the colon to anus has a higher rate of non-healing. Having the temporary
stoma acts to divert stools away from the anastomosis so that even if it does not heal properly, there would not
be any leakage of stools into the abdominal cavity and cause major complication and infection. In these cases of
temporary stoma, the stoma will be closed about 6 weeks to 3 months later.
Different Types of Colon Surgery
[1] Open Surgery
However, the incision for open surgery cuts through the entire muscle in the centre. This can give rise to more pain and would need stronger and more pain killers. Recovery after discharge is also slower. An alternative technique would be to make a small incision over the site of the tumour and perform the surgery from that location. This is only done when the exact location of the tumour is known.
[2] Minimally Invasive Surgery
This method has been used for colon resection since 1990s. There were some initial concerns about higher risk of recurrence of cancer so it did not take off in initially. However, numerous large international trials proved that there is no evidence of increased recurrence. It is now the preferred method of surgery for colon and rectum resection.
Laparoscopic surgery is technically more challenging than the standard open surgery. Three to five small incisions of 5 to 10mm each are made around the abdomen. A camera and fine instruments are then inserted through these small incisions and the surgery is performed. However, the nature of colon cancer resection is such that a small 4 to 6 cm incision is still required for the colon and the tumour to be removed.
Single Incision Port Surgery
This is one of the latest advancements in laparoscopic surgery in the last few years. A single incision of 2-5 cm is made at the umbilicus. Two instruments and a camera are inserted through this single “port” and the surgery is performed using the instruments. The colon and tumour are eventually removed through the incision.
Robotic Surgery
This is the most advanced form of minimally invasive surgery available. It is similar to laparoscopic surgery in the sense that small incisions of 5-10mm is made to insert instruments. However, the robotic camera system offers a 3-dimensional view and greater magnification to the surgeon. This gives the surgeon a clearer view as well as perception of depth which is missing in other forms of laparoscopic surgery.
The robotic instruments used are also more advanced, giving the surgeon movements similar to the wrist movements. The manipulation of the tissue is akin to using your wrist, finger and thumb, unlike standard laparoscopic surgery in which the instruments is more like using chopsticks. This advantage is especially more obvious in surgery for cancer of the rectum situated deep in the pelvis.
Non-Surgical Treatment
Chemotherapy
Radiation Therapy
FAQs About Colorectal Cancer
Is Colon Cancer Common in Singapore?
Can Colorectal Cancer Be Prevented?
- Maintaining a healthy weight and staying physically active
- Adopting a well-balanced diet rich in fibre and whole grains
- Limiting alcohol consumption and quitting smoking
When Should You Go For a Colorectal Cancer Screening?
Surgeon
Our Colorectal Cancer
Surgeon
Better Care.
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Colorectal Surgeon
Mount Elizabeth Medical Centre
#12-09, Singapore 228510
| Tel | : (+65) 6737 2778 |
| Fax | : (+65) 6737 2389 |
| : hokoksuncolorectal@gmail.com |
| Mon - Fri | : 9am - 1pm, 2pm - 5pm |
| Sat | : 9am - 1pm |
| Closed | : Sunday, Public Holiday |