The Colon and Rectum

Colon and Rectal Cancer or Colorectal Cancer is the top cancer in Singapore. The number is increasing and has become the commonest cancer in recent years. The lifetime probability of an individual developing colorectal cancer is approximately 1 in 20, and is among the highest in the world. A big proportion of patients are still diagnosed at the advanced stage of the disease. This is a tragedy because most cases are curable if they are diagnosed early. The cure rate for localised colon cancer can be as high as 90%.


What is cancer of the colon and rectum?

The colon is the last part of the digestive system where the waste material is stored. The rectum is the end of the colon adjacent to the anus. Tumours of the colon and rectum are abnormal growths arising from the cells lining the inner wall of the large intestine.

Benign tumours of the large intestine are called polyps. Benign polyps can be easily removed during colonoscopy and are not life threatening. If they are not removed from large intestine, they can become malignant (cancerous) over time. Most of the cancers of the large intestine are believed to have developed from polyps.

Who is at risk?

Though colorectal cancer may occur at any age, about 90% of the patients are over age 50. Besides age, other risk factors include:

  • Family history of colorectal cancer
  • Chinese has a higher risk among the races in Singapore
  • Personal history of colorectal polyps or cancer or ulcerative colitis
  • Cancers of other organs especially of the breast or womb or ovaries
  • Sedentary lifestyle and obesity
  • Diet high in animal fat or meat cooked at high temperatures
  • Smoking and alcohol consumption

What are the symptoms of colorectal cancer?

In the initial stages, you may not have any symptoms at all. Early symptoms of colorectal cancer may be very subtle and may include the following:

  • Blood in the stools
  • Change in usual bowel habit (e.g, constipation or loose stools)Abdominal pain and tenderness or bloatedness
  • Weight loss with no reason
  • Anaemia (low blood count)
  • A feeling that the bowel does not empty completely even just after having a bowel motion

How can colorectal cancer be prevented?

Two possible strategies may be adopted.
Firstly, reduce your risk factors if possible:

  • Reduce fat intake, especially from animal sources such as red meat. Reduce eating meat cooked at high temperatures
  • Limit alcohol intake and quit smoking
  • Exercise regularly and stay physically active
  • Eat fruits, vegetables and whole grain which contain fibre and antioxidants

Secondly, participate in colorectal cancer screening. Most colon and rectal cancer are believed to have developed from polyps. Colonoscopy detection and removal of polyps result in a reduced colorectal cancer risk. A polyp removed is a potential cancer prevented. In the United States and Northern European countries, colorectal cancer deaths has been falling, and this has been attributed to screening, early detection, prevention by polypectomy, and improved treatment.

  • It is advisable to go for a colon check from the age 50 years old to detect colorectal polyps or cancer, even if you have no symptoms.
  • Patients can be reassured that regularly scheduled (depending on your risk factors assessment) colonoscopy examinations can remove polyps and prevent development of cancer. Read more about Screening for Prevention of Colorectal Cancer

How does colorectal cancer spread?

Colorectal cancer cells can grow deep into the wall of the colon or rectum and into the fatty tissue around the colon and rectum. Colorectal cancer can also spread through the lymphatic channels to the neighbouring lymph glands. In some cases, the cancer cells spread via the blood vessels to other parts of the body such as the liver or the lungs.

How is colorectal cancer diagnosed?

Persons who have any of the risk factors such as family history or aged above 50 years should begin screening for colorectal cancer. These tests are used to detect polyps, cancer or other problems, even when the person does not have any symptoms.

If you already have any of the symptoms mentioned above, you should seek medical attention. Your doctor will conduct a detailed medical review and a physical examination and if deem necessary recommend tests including blood tests and a colonoscopy. A colonoscopy is a long thin flexible telescope with a built-in light source; it is passed through the rectum into the colon. Colonoscopy can identify abnormalities in the colon, remove polyps and take tissue for biopsy. Colonoscopy is done as a day-case procedure in the endoscopy centre. Read more about Colonoscopy

If a cancer is already confirmed, further tests such as blood tests and CT scan of the body are performed to assess the stage of the cancer. Staging is a process that tells the doctor the extent of the cancer. Staging is based on the depth of invasion of the cancer, whether lymph glands contain cancer, and whether the cancer has spread from the original site to other parts of the body. The outlook for colorectal cancers depends to a large extent on their stage.

How is colorectal cancer treated?

Surgery is the most important treatment for colorectal cancer and in most cases results in a complete cure. Radiation therapy and chemotherapy are sometimes used in addition to surgery.

During surgery, the surgeon removes the section of the large intestines that contains the cancer. All the neighbouring lymph glands will also be removed because if the cancer is to spread, it often spread to the lymph glands first. The remaining ends of the intestine will be re-connected. If the cancer is too close or has invaded the anus, the colon cannot be joined; an artificial opening on the abdominal wall for the colon, called a colostomy (or stoma), may be required. This opening allows waste to be removed from the body when the anus cannot be used or has to be removed. A colostomy may be temporary or permanent.

With advances in modern technology in surgery, more than 95% of all colorectal cancer patients do not require a permanent colostomy. The most important factor in determining if the anus is required to be sacrificed is the clearance gap between the cancer and the top of the anal canal, the differentiation grade of the cancer, the extent and size of the cancer. In some cases, a temporary stoma may be created for diversion of the flow of the waste to allow the joint to heal. When the area has fully recovered, a second minor operation is done to close the stoma.

Surgery for colon and rectal cancer

Standard Open Surgery

Standard open surgery requires a long incision on the abdomen. Surgery involves the removal of a segment of the colon and/or part of the rectum, together with its blood supply and lymph nodes. The healthy ends are then joined together to form an anastomosis thereby restoring continuity of the digestive tract. The average hospital stay is about 1 week depending on the patient recovery.

Laparoscopic (Keyhole) Surgery

Laparoscopic (Keyhole) surgery uses small keyhole incisions on the abdominal wall and the operation is performed using specialised long instruments and a surgical camera. The exact same procedure as in standard open surgery is done internally with the use of keyhole instruments to remove the affected segment of large bowel together with its blood supply and lymph nodes. The healthy ends are then joined together to restore continuity of the digestive tract. The operative steps are similar to open surgery with the advantage of having smaller wounds, shorter hospital stay and quicker recovery period. Dr Quah is proficient in laparoscopic surgery. Laparoscopic colorectal surgery is performed here routinely.

What is the outlook for colorectal cancer?

Between 80%-95% of colorectal cancer patients are cured if the cancer is detected and treated in the early stages. The cure rate drops to 50% or less when diagnosed in the later stages. Screening is the detection of colorectal cancer in its early stage or polyps (which have not transformed into cancers) when there are no symptoms. By the time symptoms develop, some patients with cancer diagnosed are already in the later stages.

The earlier the person receives treatment, the greater the chance of cure. Improvement in surgical techniques and better nursing care mean that surgeons can now operate on people with low complication rates as well as people who were once considered too old for operation or when the cancer was thought to be too advanced.