Colorectal Cancer

Colorectal Cancer - What it is

Colorectal cancer is a disease that begins in the colon or rectum. The colon is responsible for absorbing water and salts from the food that we eat and turns indigestible food into waste. The rectum is the part of the large intestine that connects the colon to the anus and stores food waste of the body. Colorectal cancer occurs when cells of the colon or rectum develop genetic mutations that cause cells to grow uncontrollably and form malignant tumours.

Most colorectal cancers begin as polyps, which are benign growths on the inner lining of the colon or rectum. Polyps may be small and generally do not cause any symptoms. Over time, some of these polyps can change and become cancerous.

Cancer cells from the inner lining can grow deep into the wall of the colon or rectum and may extend into the surrounding fatty tissue and organs. Colorectal cancer can also spread to nearby lymph nodes. In some cases, cancer cells spread through blood vessels to other parts of the body such as the liver and lungs.

Colorectal Cancer - Prevalence

Colorectal cancer is the second most common cancer in Singapore, affecting 36 out of 100,000 people¹. It is the second most common type of cancer for men and women after prostate cancer and breast cancer, respectively. Between 2018-2022, 12,704 cases of colorectal cancer were diagnosed in Singapore.

Colorectal cancer is commonly diagnosed in people aged 50 years and above though a rising incidence amongst younger individuals under the age of 50 has been noted globally.

Younger individuals who are diagnosed with colorectal cancer may have hereditary conditions including familial adenomatous polyposis (FAP) or hereditary non-polyposis colorectal cancer. Commonly, younger onset colorectal cancers may also be sporadic (non-hereditary) with multiple environmental and lifestyle factors contributing to its development.

Regular screening tests are recommended to help prevent colorectal cancer by identifying and removing polyps before they turn cancerous.

Colorectal Cancer - Symptoms

In early stages, colorectal cancer may not have any noticeable symptoms. In later stages, symptoms may include:

Persistent diarrhoea or constipation
Blood in the stools or rectal bleeding
Persistent change in the consistency of stools
General abdominal discomfort (bloating, fullness, cramps or gas)
A feeling that the bowel does not completely empty after opening the bowels
Constant tiredness
Severe appetite or weight loss

The symptoms above can be caused by a number of reasons and may not indicate the presence of cancer. However, make an appointment with your doctor if you have any signs or symptoms that worry you.

Colorectal Cancer - How to prevent?

Regular screening is the best way to detect colorectal polyps or cancer early. In Singapore, the recommended age of screening for colorectal cancer is 50 years old for individuals with no symptoms. Individuals with a family history of colorectal cancer are advised to start screening earlier. Speak with your healthcare provider who will be able to do a risk assessment and advise you on screening recommendations.

Routine screening tests include:

Faecal Immunochemical Test (FIT) (yearly)

Blood in the stool may be an early sign of colorectal cancer. FIT is used to detect the presence of human blood in the stool. If blood is found, additional tests would be performed to evaluate the source of bleeding and the presence of cancer.

Colonoscopy (every 5-10 years)

During this procedure the colon and rectum are examined using a special flexible camera inserted through the anus. It allows the removal of small polyps and biopsy of any abnormal areas.

In addition to regular screening, a healthy lifestyle may help to prevent colorectal cancer and includes:

Eating a diet rich in fruit, vegetables and whole grains
Limiting the consumption of red meat and processed meats
Quitting or not starting smoking
Limiting alcohol consumption
Regular exercise and maintaining a healthy weight

Colorectal Cancer - Causes and Risk Factors

The exact cause of colorectal cancer is not known but certain risk factors such as age, having certain medical conditions, inherited genetic syndromes, diet and lifestyle can contribute to the development of colorectal cancer.

Having risk factors increases the likelihood of developing the colorectal cancers but it does not guarantee that the condition will develop. Understanding risk factors can help with prevention and recommended screening.

Factors that can increase the risk of colorectal cancer include:

Older age – Colorectal cancer is often diagnosed in people aged 50 years and above. However, younger people can also be diagnosed with the cancer.
History of colorectal polyps or cancer – Having colorectal polyps or cancer in the past increases the risk of developing colorectal cancer.
Inflammatory bowel diseases – Having ulcerative colitis, Crohn’s disease or other diseases that cause inflammation of the intestines can increase the risk of developing colorectal cancer.
Family history of cancer or conditions – Having one or more blood relatives, who have had colorectal cancer or an inherited condition such as Lynch syndrome or familial adenomatous polyposis, increases the risk of developing the disease.
Diabetes - Having diabetes and insulin resistance elevates the risk of developing colorectal cancer.
A low-fibre, high fat diet – Some research has shown that eating a diet low in fibre and high in fat and calories, a typical Western diet, increases the risk of developing colorectal cancer.
A sedentary lifestyle – Being inactive and not engaging in regular physical activity can increase the risk of developing the disease.
Smoking – As with most cancers, smoking is a risk factor for developing colorectal cancer.
Heavy use of alcohol – Drinking copious amounts of alcohol can increase the risk of colorectal cancer.

There are some complications that may arise as colorectal cancer progresses and even after treatment. These include:

Bowel obstruction can happen when the tumour grows and blocks the intestines
Low blood counts may result from blood losses from bleeding tumours
Cancer spread or metastases to other organs, such as the liver, lungs, peritoneum and lymph nodes.
Cancer recurrence is when cancer develops again after initial treatment and remission. A recurrence may develop at the same site of the previous colorectal cancer or may spread and develop in other organs.

Colorectal Cancer - Diagnosis

There are several different tests that can be used to detect polyps, cancer or other abnormalities in the colon and rectum. Before administering some of these tests, the colon must be emptied, and the doctor may prescribe an enema or a liquid laxative. This preparation is very important in ensuring the test accuracy.

Diagnostic tests include:

Digital rectal examination

Often part of a routine physical examination during a clinical consult, the doctor checks the lower most area of the rectum by inserting a lubricated gloved finger into the rectum and gently feeling for abnormal growths. The exam may be uncomfortable but should not be painful.

Colonoscopy

Part of regular screening and diagnostic procedures, a colonoscopy examines the colon and rectum using a special flexible camera inserted through the anus. It allows the removal of small polyps and taking of tissue samples (biopsies) of any abnormal areas.

Computed Tomographic Colonography (CTC)

A CTC or virtual colonoscopy is a specific scan that creates a 3D image of the colon to reveal any abnormal masses. Images are taken seconds after the colon is inflated with carbon dioxide through a small rectal tube.

If diagnosed with colorectal cancer, the doctor may recommend further tests to determine the extent or stage of cancer. These are usually imaging tests for the abdominal, pelvic and chest areas.

In some cases, the extent of the cancer will only be known after surgery.

Colorectal Cancer – Staging

Stage 0 Carcinoma in situ – When there are abnormal or precancerous cells found in the mucosa, or innermost lining of the colon or rectum.

Stage 1 Colorectal Cancer – When cancer has spread into the deeper layers of the intestinal wall but does not extend beyond the muscle layer.

Stage 2 Colorectal Cancer - When cancer has penetrated deeper through or beyond the muscle layer of the intestine wall but has not spread to nearby lymph nodes.

Stage 3 Colorectal Cancer – When cancer has spread to the surrounding regional lymph nodes.

Stage 4 Colorectal Cancer – When cancer has spread or metastasised to areas beyond the colon or rectum and other organs such as the liver, lungs and perineum.

Colorectal Cancer - Treatments

Treatment for colorectal cancer depends on the stage, location, size, and histopathological features such as the grade of the cancer.

An individual with colorectal cancer should be assessed by a multi-disciplinary team of specialists to determine which modality of treatment is best suited for them. Colorectal cancer treatment requires the involvement of different specialists – surgeons, medical oncologists, radiation oncologists, radiologists, nuclear medicine physicians, and palliative medicine specialists. Such multi-disciplinary care is available at SingHealth healthcare institutions.

Types of treatment:

Surgery

Depending on the stage of cancer, there are different approaches that the surgeon may use during surgery.

In very early stages colorectal cancer the surgeon may only remove the cancerous growth or polyps involving only the innermost lining of the colon in a procedure called a polypectomy.

In more advanced stages, the surgeon may remove a section of the colon or rectum that has a tumour and some surrounding tissue which includes regional lymph nodes. The remaining healthy bowels are then reconnected.

When the healthy colon cannot be reconnected during the initial surgery, surgeons perform a stoma creation by creating an opening for the colon (or small intestines) onto the surface of the abdominal wall. A colostomy (opening in the colon) or an ileostomy (opening in the ileum small intestines) allows food waste to be removed from the body that is in then collected in a stoma bag. A stoma may be temporary or permanent. Specialist nurses are available to help patients or their caregivers with stoma maintenance and care.

Minimally invasive surgery or laparoscopic surgery, where the surgeon performs the operation through several small incisions in the abdominal wall, may be performed. This method has been shown to minimise pain after surgery and accelerate recovery but is not suitable for all cases of colorectal cancer.

Sometimes, chemotherapy and/or radiotherapy may be used before or after surgery.

Increasingly, some patients with stage 4 cancer with limited spread to the liver, lung or peritoneum (oligometastatic disease) may be suitable for surgical treatments that can provide long term disease control or even cure. Our colorectal surgeons and oncologists work closely with the liver, lung and peritoneal surgeons to coordinate surgical treatments in patients with limited spread to the other organs for which curative intent surgery may still be possible.

Chemotherapy and/or targeted therapy

Chemotherapy is the use of anti-cancer drugs to destroy cancer cells. The type of chemotherapy, how it is administered, and the number of cycles required, depends on the type and stage of cancer, how well the patient responds and the side effects of treatment. Molecular profiling of the tumour is often performed to characterise each patient’s cancer to assist in selecting the medications that a patient is more likely to respond to. There are now more systemic treatment options including targeted therapy and immunotherapy, explained in more detail below.

In patients with stage 2 and stage 3 cancer, chemotherapy (oxaliplatin, fluoropyrimidines) may be given after surgery for up to 3-6 months, to reduce the risk of recurrence and increase chances of long-term survival. Patients will be followed up for 5 years with regular physical examination, blood tests and interval radiological imaging, plus colonoscopy as indicated.

In stage 4 disease where the cancer has spread to other organs, chemotherapy and/or targeted therapy is given to control the cancer in order to shrink the tumour, and to control the spread of cancer cells. Some treatments include chemotherapy (oxaliplatin, irinotecan and fluoropyrimidines, TAS102), anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (panitumumab, cetuximab), anti-vascular endothelial growth factor (VEGF) monoclonal antibodies (bevacizumab, ramucirumab) and oral tyrosine kinase inhibitors such as encorafenib and regorafenib. On top of systemic therapy, some patients with oligometastatic disease may also be amenable to further surgical resections and/or other locoregional therapies such as ablation and radiation. Newer treatments and clinical trials may be available for some patients, and these can be discussed with your medical oncologists.

Some side effects may be experienced with systemic treatment (mouth sores, rashes, numbness, loss of appetite, nausea/vomiting, diarrhoea, low blood counts, infections, allergic reactions and rarely organ dysfunction) but your condition will be monitored closely by your oncologists and adjusted as necessary. We also have a strong support from palliative care services, medical social services, physiotherapists, oncology specialist nurses and pharmacists that can help patients along their treatment journey.

Radiation therapy

Radiation or radiotherapy uses high-energy X-rays to kill cancer cells. The aim of radiotherapy is to destroy a localised area of cancer cells and spare as many normal cells as possible. Radiation therapy is sometimes used after surgery for colorectal cancer to destroy any remaining cancer cells and prevent the cancer from recurring. It may also be used to reduce the size of the rectal cancer before surgery.

In some cases, when surgery is not an option, radiation therapy is used to control the growth of tumours which are causing pain or bleeding.

Immunotherapy

Immunotherapy is a treatment that uses the patient’s own immune system to fight cancer. It is given intravenously and is usually used in selected cases of patients with microsatellite instability high (MSI-H) or deficient mismatch repair (dMMR) colorectal cancers. MSI-H/dMMR colorectal cancer may be linked to a hereditary type of colorectal cancer syndrome called Lynch Syndrome or may be sporadic (non-hereditary).

Supportive (palliative) care

Palliative care is specialised medical care that provides relief from pain and symptoms of serious illness so that a person with cancer feels better and has a better quality of life. The palliative care team of doctors, nurses and other healthcare professionals provide an additional layer of support that complements ongoing care.

Colorectal Cancer - Preparing for surgery

Your surgeon will perform a comprehensive medical work-up including blood tests and scans to see if you are suitable for surgery and advise you on the risks involved. Patients with complex conditions that require multimodality treatments may be discussed amongst various specialists, at a multidisciplinary tumour board, for a consensus treatment recommendation that weighs the pros and cons of every treatment strategy.

Before surgery, the anaesthesia team will also assess your fitness for surgery and advise you on various aspects of general anaesthesia and pain control after surgery. Specialist nurses will also provide pre-surgery counselling.

Colorectal Cancer - Post-surgery care

After recovering from surgery, you will be given regular outpatient appointments to see your team of doctors. These visits may include blood tests and scans to monitor and check if the cancer recurs. You may be referred to other specialists should you require further treatment after the surgery.

It is important to follow your doctor's advice, keep to scheduled clinic visits and do the prescribed tests so that timely treatment can be administered if the cancer or other problems arise.

Colorectal Cancer - Other Information

What is colorectal cancer?
Colorectal cancer is a type of cancer that starts in a part of the intestine called the colon or rectum. It is sometimes referred to as colon cancer or rectal cancer, depending on where it starts.
What causes colorectal cancer?
The exact cause of colorectal cancer is not known, but it commonly develops from polyps in the colon or rectum, which can become cancerous over time. Genetic mutations, both inherited and acquired, environmental and lifestyle factors may also play a role in the development of colorectal cancer.
What are the symptoms of colorectal cancer?
Symptoms can include changes in bowel habits (such as diarrhoea or constipation), blood in the stools, abdominal pain or cramping, unexplained weight loss and a feeling that the bowel does not empty completely.
Is colorectal cancer hereditary?
Some cases of colorectal cancer are hereditary, particularly those associated with genetic syndromes like Lynch syndrome or familial adenomatous polyposis (FAP). Family history is an important factor in assessing risk.
Can colorectal cancer be cured?
Yes, colorectal cancer can be cured when it is diagnosed and treated when localised (stage I-III). It is therefore important for individuals 50 years old and above, or those with risk factors to undergo colorectal cancer screening for early detection. With medical advancements, treatment may also be potentially curative for a smaller subset of patients with stage IV colorectal cancer that has limited spread amenable to surgery or ablation.

¹Chen, H. L. R., Chong, Q. D., Tay, B., Zhou, S., Wong, E. Y. T., Seow-En, I., Tan, K. K., Wang, Y., Seow, A., Tan, K. E., Tan, B. H. I., & Tan, S. H. (2025). Trends in Early-Onset Colorectal Cancer in Singapore: Epidemiological Study of a Multiethnic Population. JMIR public health and surveillance, 11, e62835. https://doi.org/10.2196/62835

SingHealth experts share more about colorectal cancer:

For more information, click here for the English publication on Colorectal Cancer.
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For further enquiries on Colorectal Cancer, please call the Cancer Helpline at (65) 6225 5655 or email to [email protected]

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Overview

Article contributed by National Cancer Centre Singapore;Singapore General Hospital;Changi General Hospital;Sengkang General Hospital;KK Women's and Children's Hospital

The information provided is not intended as medical advice. Terms of use. Information provided by SingHealth

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