Patient guide
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Colorectal cancer is cancer of the colon and rectum, also known as bowel cancer. It is the second most common cancer in Singapore in both men and women.1 It usually begins as polyps in the lining of the colon or rectum. Most polyps are benign, but some can become cancerous, and removing them early can prevent colorectal cancer.
Around 1,200 new cases are diagnosed in Singapore each year.2 Most colorectal cancers begin as adenomatous polyps, and the change from polyp to cancer takes 5 to 10 years, which is what makes prevention possible.2
That slow change leaves a long window in which a polyp can be found and removed. About 90% of polyps can be removed during a colonoscopy, which avoids the need for surgery.2
Nobody knows exactly why a cell becomes cancerous, but it is thought that the genes in the cells are damaged or altered, triggering the cells to grow uncontrollably.
Non-modifiable risk factors include:
Risk can be lowered by:3
If colorectal cancer is suspected, your doctor may order:
If a suspicious area is found, tissue samples are taken during colonoscopy and examined under a microscope. If cancer is confirmed, staging with a CT scan and blood tests determines the extent of spread and guides treatment.
Surgery is the foundation of curative treatment. The diseased section of the colon or rectum is removed, along with the nearby lymph glands, to reduce the risk of the cancer spreading.3 In early-stage cancer, surgery can cure most patients. In advanced cases, surgery can still improve quality of life.
Keyhole surgery is possible in suitable cases. Laparoscopic surgery, done through several small incisions in the abdominal wall, has been shown to reduce pain after surgery and speed up recovery, though it is not suitable for every case.3
Some operations require a stoma. This is an opening that allows waste to leave the body when the normal route cannot be used or has had to be removed, and it may be temporary or permanent.3 Many people having surgery for colorectal cancer do not need one.
Anyone with colorectal cancer should be assessed by a multidisciplinary team of specialists, who agree on the treatment plan together.3 Dr Chen will explain what that means in your case.
More on colorectal cancer surgery →
Depending on the stage of the cancer, chemotherapy, radiotherapy or a combination may be needed. These may be given after surgery (adjuvant therapy) to kill cancer cells that escaped the primary tumour, or occasionally before surgery to shrink the cancer for a better outcome.3
For stage 2 and stage 3 cancer, chemotherapy is usually given after surgery for three to six months, to reduce the risk of the cancer returning.3 Radiotherapy is used mainly for rectal cancer.3 In stage 4, chemotherapy, sometimes with targeted therapy, is used to shrink the tumour and control the spread of the cancer.3
After treatment you are followed up for 5 years, with regular examinations, blood tests and scans, plus colonoscopies as needed.3
Staging describes how far the cancer has grown through the bowel wall and whether it has reached the lymph nodes or other organs. It is the single biggest factor in deciding treatment. Scans give a first estimate before surgery, but the stage of cancer present is only confirmed once the removed tissue has been examined under a microscope.
In broad terms, earlier stages are confined to the bowel wall, middle stages involve nearby lymph nodes, and the most advanced stage means spread to one or more other organs. Chemotherapy after surgery is used for stage 2 and stage 3 cancer, to reduce the risk of the cancer returning.3
Screening with colonoscopy can detect early-stage cancer and give a better chance of cure. In some cases it can prevent colorectal cancer by removing polyps or suspicious growths before they turn cancerous.
Screening is recommended from age 50 for people without risk factors, by colonoscopy every 5 to 10 years or a stool test annually.2 Where there is a family history it starts earlier and is repeated more often, as set out on the colorectal cancer screening page.
The stool test has a real limitation. An estimated 50% of cancers are missed on each round,2 It is repeated every year for that reason, and a colonoscopy is the more thorough option where it is appropriate.
See a doctor if you have bleeding from the back passage, a change in bowel habit that has persisted, unexplained weight loss, persistent abdominal pain or bloating, or anaemia found on a blood test.
If you are 50 or older and have never been screened, it is worth discussing screening even with no symptoms present, since early colorectal cancer frequently causes none.
It is the second most common cancer in Singapore, with around 1,200 new cases diagnosed each year.2 It is also one of the few common cancers that screening can prevent rather than only detect early.
No. Most polyps are benign. Most colorectal cancers do begin as adenomatous polyps, and the change takes 5 to 10 years,2 and polyps are removed upon discovery. About 90% can be removed during the colonoscopy itself.2
Surgery is the foundation of curative treatment, and in early-stage cancer it can cure most patients. Outcomes depend heavily on the stage of cancer at diagnosis, which is not known until the removed tissue has been examined. Dr Chen will discuss what your own results mean.
Many people having surgery for colorectal cancer do not. A stoma is an opening that allows waste to leave the body when the normal route cannot be used or has had to be removed, and it may be temporary or permanent.3 Dr Chen will tell you beforehand if one is likely in your case.
That depends on the confirmed stage. For stage 2 and stage 3 cancer, chemotherapy is usually given after surgery for three to six months, to reduce the risk of the cancer returning.3 For rectal cancer, radiotherapy may be given beforehand to shrink it.3 In stage 4, chemotherapy, sometimes with targeted therapy, is used to shrink the tumour and control the spread of the cancer.3
You are followed up for 5 years, with regular examinations, blood tests and scans, plus colonoscopies as needed.3 The purpose is to pick up any recurrence, and to find new polyps before they become a problem.
BUILD NOTE: Dr Chen’s original text is preserved throughout; the added sections and all cited figures have NOT yet been read by him. Both sources were fetched and checked on 22 September 2026, and the NCCS page shows no review date. This page deliberately publishes no survival percentages by stage. The sentence “surgery can cure most patients” is Dr Chen’s original wording and is the strongest claim on the site; it needs his explicit sign-off before cutover.
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