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colorectal cancer logoWhat Is Colorectal Cancer?

Colorectal cancer is cancer of the colon and rectum (or the large intestine), which is the last part of the gastrointestinal tract. When food enters the colon, water is absorbed and the food residue is converted into waste (faeces) by bacteria. The rectum is the terminal part of the colon that stores faeces before it is expelled through the anus. Polyps may form on the inner wall of the colon and rectum. These are benign lumps which are fairly common in people above the age of 50. However, certain types of polyps may develop into cancer and should be removed if they are detected. 

Certain characteristics of a polyp may indicate malignancy:

  • Polyps greater than 1 cm in diameter
  • Sessile polyps (i.e. polyps without a stalk)
  • Multiple polyps

In the early stages of colorectal cancer, the cancer cells are confined to the colon. If undetected, the cancer will develop and project into the lumen of the colon. It will also invade through the colon wall and spread by:

  • Invading neighbouring intestines and organs
  • Entering the lymphatic system and travelling into neighbouring lymph glands (mesenteric lymph nodes)
  • Entering the blood stream and travelling to the liver where secondary malignant deposits may form

Risk Factors

elderly couple1. Age
Men and women aged 50 years and above have an increased risk of colorectal cancer

2. Ethnicity
Among the races in Singapore, the Chinese have a higher risk of colorectal cancer.

3. Personal History

Individuals who have been detected with colorectal polyps or diagnosed with colorectal cancer in the past may be at a higher risk of experiencing a recurrence and are advised to seek regular screening.

4. Family History

Some individuals inherit a rare disease called familial polyposis in which many colorectal polyps develop at a young age. For these individuals, the risk of developing colorectal cancer is very high (80 to 100%). Such individuals should consider having the colon removed before the age of 40. Individuals who have relatives with polyps or colorectal cancer are also at a higher risk of colorectal cancer although this risk is lower compared to one with familial polyposis.

5. Ulcerative Colitis 

This is a disease affecting the bowels which, in the long term, leads to inflammation and cancerous changes. People with with this condition have a significant risk of colorectal cancer.

6. Drugs

Current users of HRT (hormone replacement therapy) are at a lower risk of colorectal cancer, although this protection disappears within 5 years of stopping HRT. Aspirin and NSAID (a strong painkiller drug) are known to reduce the risk of colorectal cancer. However, it is premature to recommend the routine use of these drugs for this purpose.

7. Sedentary lifestyle and obesity

These interrelated factors increase the risk of colorectal cancer. However, physical activity improves the movement of faeces in the colon and can reduce risk.

8. Dietary Habits

Research has identified certain factors which can affect the risk of colorectal cancer:



Dietary Factors that may Increase Colorectal Cancer Risk Dietary Factors that may Reduce Colorectal Cancer Risk
Processed and red meat  Fruits and vegetables
Meat cooked at high temperatures Dietary fibre


Despite knowledge of these risk factors, the exact cause of colorectal cancer is unknown. It is estimated that 50 per cent of colorectal cancer patients have no known risk factors.



Laproscopic Colon Surgery (also known as Keyhole Surgery)

Colorectal cancer has been treated using this minimally invasive technique. Its advantage is less pain and quicker post-operative recovery. However, it is technically difficult, time consuming, and expensive to carry out. Laparoscopic surgery might not be the best approach for everyone. Please discuss with your doctor if you are considering this type of surgery.



Chemotherapy is the administration of toxic drugs to kill cancer cells which may be found at the site of the cancer or elsewhere in the body after surgery. It is indicated for patients with advanced colorectal cancer at stages II, III or IV after surgery and improves survival rates.

Chemotherapy usually involves the weekly injection of a cytotoxic drug called 5FU (5 Flurouracil) alone or in combination with other drugs for up to a year.

Because of its toxicity, chemotherapy causes significant side effects. The immediate side effects include nausea, vomiting, diarrhoea, susceptibility to infection, low white cell counts, and hair loss. The long-term side effects include premature menopause and risk of a second cancer.



Radiotherapy is the administration of powerful radioactive rays to treat cancer. Its role in the treatment of colorectal cancer is secondary to surgical excision and is used in the following situations:

  1. After the surgical removal of a colorectal cancer which has invaded the adjacent organs and/or nearby lymph nodes to destroy residual cancer cells within the site of the cancer.
  2. During the pre-operation phase, it is used on a locally advanced rectal cancer to shrink it to a size where it can be surgically removed.

Radiotherapy is administered in daily sessions, 5 days per week over 4 to 6 weeks. Side effects are usually tolerable and temporary and range from abdominal cramps and pain, constipation or diarrhoea, cystitis, excoriation of perianal skin, and generalised tiredness.


Pre-Operation Preparation

Colorectal cancer surgery is a major operation. Careful preparation before the operation is of the utmost importance.

  • Individuals above the age of 70 or those with chronic diseases such as diabetes, hypertension, and stroke as well as liver, heart, lung, or kidney problems) are at a higher risk from undergoing surgery and general anaesthesia. Their fitness will be carefully assessed for surgery and general anaesthesia.
  • Preparations:

    Patients who have:

    Pre-operation Preparations:

    Poor lung function or smoke

    Smoking cessation

    Breathing exercises

    Ischaemic heart disease and are on anti-platelet therapy

    Cardiac assessment

     Stop taking anti-platelet drugs


    Albumin transfusion

    Hypertension or diabetes mellitus

    Careful manangement of blood pressure or blood sugar levels before the operation

  • The patient's colon is cleansed of faeces before the operation to prevent contamination at the time of surgery. The patient is admitted before the operation and given purgatives. Patients are only permitted a liquid low fibre diet for a few days before the operation.
  • As colorectal surgery involves coming into contact with faeces, a strong antibiotic is administered before the operation.


Post-Operation Period

This crucial period lasts about one week long as the patient recovers from the operation. The patient may develop a complication such as a lung infection or leakage from the anastomosis. He/she may be put on an intravenous drip to supply fluids. After recovering intestinal function and the ability to eat and drink, the intravenous drip is stopped. Medication needed during this period includes antibiotics and strong painkillers.