Colorectal Cancer: Essential Facts and Screening Insights

Contributed by: Dr Foo Kian Fong

Colorectal cancer is the most prevalent type of cancer affecting Singapore's population. Are you considering a colonoscopy screening? Here is what you need to know.

Masterclass Speakers

Dr Foo Kian Fong
Senior Consultant, Medical Oncology
Parkway Cancer Centre

Dr Calvin Koh
Gastroenterologist & Physician
The Gastroenterology Group

Dr Leonard Ho
Senior Consultant, Colorectal Surgeon
One Surgical Clinic & Surgery

In 2014, Mr Wong* ought medical advice due to bloating and changes in his bowel habits. Tests revealed he had an intestinal obstruction caused by Stage 4 colon cancer. Unfortunately, his situation is not rare. In Singapore, over 50% of colorectal cancer patients are diagnosed at an advanced stage. This is particularly concerning as colorectal cancer is not only widespread globally but also the second leading cause of cancer deaths in Singapore.

Colorectal cancer affects the colon, large intestine and rectum. It originates from mutations in DNA, with age being a primary factor. Cells that divide actively accumulate harmful mutations over time. Colorectal cancer develops through a sequence of mutations where normal tissue in the colon or rectum lining turns into a polyp, which then may progress to cancer over several stages.

To enhance understanding of colorectal cancer, Dr Calvin Koh, Gastroenterologist at The Gastroenterology Group; Dr Leonard Ho, Senior Consultant at One Surgical Clinic & Surgery; and Dr Foo Kian Fong, Senior Consultant, Medical Oncology, at Parkway Cancer Centre, shared their expertise at the Colorectal Cancer Insights Masterclass, held on 4 May 2024 at Gleneagles Hospital Lecture Theatre.

Recognising the Symptoms

“Early colon cancer often presents no symptoms,” said Dr Koh. “Symptoms are often a sign of more advanced disease.” These include bowel obstruction symptoms like constipation and abdominal cramps, or systemic symptoms such as weakness, fatigue, and unexplained weight loss due to anaemia or cancer-secreting chemicals.

Dr Koh notes that these symptoms are common and non-specific. Thus, not everyone experiencing them will have colorectal cancer.

Who is at Risk?

Diet plays a significant role in colorectal cancer risk, especially the intake of processed and red meats. For example, consuming processed meat 10 servings a week can increase your risk by about 20%. Other risk factors include excessive alcohol consumption, smoking, a sedentary lifestyle and obesity. Family history and inflammatory bowel diseases like Crohn's disease or ulcerative colitis also increase the risk significantly. Age is the most substantial risk factor, with individuals aged 70 being at four times the risk compared to those who are 40.

Lifestyle Changes and Prevention

While some risk factors like family history and age are unchangeable, others related to lifestyle can be modified. Reducing consumption of red and processed meats, eating more fruits and vegetables, and regular exercise can mitigate some risks. High-risk individuals should also consider regular screenings.

Screening and Detection

Screening is crucial for early detection. The development of a small polyp to cancer takes about 10 years. This allows doctors a chance for intervention. “During colonoscopy, if we see a polyp, we take it out and prevent further progression of the disease. Colon cancer is a preventable disease,” highlighted Dr Koh.

In Singapore, the recommended age to begin colorectal cancer screening is 50 for those without symptoms. Dr Ho advised people with a family history of the disease to consider screening at an earlier age.

Screening options include:

  • Faecal Immunochemical Test Kit (FIT): This simple test can detect blood in the stool. Kits can be obtained from the Singapore Cancer Society and pharmacies. If test results come back as positive, further testing is required.

  • Colonoscopy: This is the gold standard for colorectal screening. During a colonoscopy, the specialist inserts a fibre optic tube (known as a colonoscope) into the anus and advances it through the large intestine to reach the caecum. The scope is then withdrawn.

    During withdrawal, the colon and rectum are assessed for conditions such as polyps. Should a polyp be found, the specialist will remove the polyp and send it for further histological (microscopic) examination. Most polyps can be successfully removed during a colonoscopy. Polyps which are found to be too large or advanced will have to be removed using other techniques. Many patients have a phobia of undergoing a colonoscopy, as they imagine it to be uncomfortable and requires bowel preparation.

    Dr Ho explained that under the care of an experienced proceduralist/specialist, the discomfort is minimal. However, undergoing bowel preparation is still a compulsory step in preparing for a colonoscopy. “This step is essential; it allows the specialist to make a meaningful assessment,” explained Dr Ho. He adds that if the colonoscopy is normal, a person does not need a repeat procedure for the next seven to 10 years.

  • CT Colonography: This is a type of CT scan (computed tomography scan) that provides detailed images of the colon and rectum. Should abnormalities be detected in the CT images, the patient is required to undergo a colonoscopy. If the results of the CT Colonography are normal, the patient is not required to undergo colonic evaluation for the next five years. Like colonoscopy, bowel preparation is required for CT Colonography.

Treatment Options

Colorectal cancer is treated through surgery, chemotherapy and radiation, often in a multidisciplinary approach for advanced cases.

The standard surgical method is surgery. Currently, many surgeons perform keyhole surgeries involving minimal incisions for less pain and quicker recovery.

Non-surgical treatments like chemotherapy, targeted therapy and immunotherapy are tailored based on each patient's specific conditions and genetic markers. These treatments are usually used for advanced Stage 4 cancers to control the disease for a longer period.Dr Foo offered insight into the various non-surgical approaches:

  • Chemotherapy with Curative Intent: Administered with the goal of curing the patient, this treatment is usually reserved for a rare cancer of the colon, namely lymphoma of the colon.
  • Adjuvant Chemotherapy: Designed for patients at a higher risk of cancer recurrence, particularly those in advanced stages, this treatment aims to maximise the chances of a cure.
  • Palliative Chemotherapy: For patients whose cancer has spread, and where a cure is no longer feasible, this treatment focuses on shrinking the cancer, alleviating symptoms and extending life. “Palliative Chemotherapy not only extends survival but also enhances quality of life,” Dr Foo explained. “It significantly reduces pain and boosts energy levels, as evidenced by numerous studies.”
  • Targeted Therapy: This treatment, administered either intravenously or in pill form, specifically targets cancer cells without affecting normal cells, offering a more controlled approach to managing advanced stages of colorectal cancer.
  • Immunotherapy: Leveraging the body's immune system, this treatment uses naturally occurring or lab-made substances to bolster the body's defence against cancer. This innovative approach holds promise for a small percentage of colorectal cancer with specific genetic markers, enhancing their immune response to fight cancer more effectively.

Understanding colorectal cancer and participating in regular screenings can dramatically increase the chances of prevention and successful treatment. With advancements in medical technology and treatment strategies, patients have a fighting chance for recovery and maintaining quality of life.

Ways to Prevent Colorectal Cancer

  • Reduce intake of red meat and processed meat
  • Eat more fruits and vegetables
  • Manage your weight
  • Quit smoking
  • Drink alcohol in moderation
  • Exercise regularly
  • Ensure a minimum 6 hours of sleep each night
  • Go for regular screening


* Pseudonym to protect patient privacy

POSTED IN Cancer Prevention, Cancer Treatments
TAGS adjuvant therapy, cancer mutation, cancerous polyps, colon cancer, colonoscopy, colorectal cancer, history of cancer, prevent cancer, stage 4 cancer
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