What is Colorectal Cancer?
As its name suggests, colorectal cancer is common cancer in Singapore that starts in the colon or rectum. Depending on the location where the cancer has started, it may also be known as colon cancer or rectal cancer. Colorectal cancers typically start as a growth, or polyp, found on the inner lining of the colon or rectum. If this growth becomes cancerous, it will grow into the wall of the colon or rectum over time. It may also spread to other areas of the body in a process known as metastasis.
Colorectal cancer is Singapore’s top cause of cancer death, taking more than 1,865 cases a year. Thankfully, it is highly preventable with the help of regular screening via colonoscopy.
It is also the most common cancer in Singapore males and 2nd most common in Singapore females. Dr Benjamin Yip reminds us that “ if you are 50 and above (or younger, if you have other risk factors), please speak to your Gastroenterologist regarding screening today. It might just save your life!”
Symptoms of Colorectal Cancer
Colorectal cancer may not cause any symptoms in its initial stages, but some signs and symptoms to look out for include:
- Persistent abnormal bowel habits
- Feeling like your bowels do not empty completely
- Rectal bleeding
- Blood in the stool
- Anaemia
- Abdominal pain
- Weakness
- Fatigue
- Unexplained weight loss
Please consult your gastroenterologist if you experience any of the aforementioned symptoms.
Risk Factors for Colorectal Cancer
Risk factors for developing colorectal cancer include:
- Obesity
- Physical inactivity
- Dietary habits
- Smoking
- Excessive consumption of alcohol
- Age (50 years and above)
- History of colorectal polyps
- History of inflammatory bowel disease
- Family history of colorectal cancer
- Diabetes
In Singapore, it is recommended that individuals above the age of 50 years old undergo a colonoscopy. Individuals with a family history or symptoms of colorectal cancer are advised to start screening earlier.
How is Colorectal Cancer diagnosed?
Colorectal cancer may be diagnosed in a number of ways, including:
Physical Examination
Your abdomen will be palpated to check for any masses or organ enlargement. Your doctor may also perform a digital rectal exam (DRE), where a finger is inserted into the rectum to check for any abnormal masses, or proctoscopy, where a proctoscope is inserted in the anus and rectum to check for any abnormalities.
Laboratory Tests
You may be required to submit a stool sample to check for the presence of blood in your stool. There are also certain blood tests that your doctor may choose to order, such as that to check for tumour markers. The most common tumour marker for colorectal cancer is carcinoembryonic antigen (CEA).
Diagnostic Colonoscopy
During a colonoscopy, a thin, flexible tube with a camera on one end – known as a colonoscope – is inserted into the rectum and colon via the anus. This will let your doctor check the entire length of the colon and rectum for any abnormal growths.
Diagnostic Imaging Tests
Ultrasounds, X-rays, CT scans, or MRI scans may be used to further examine any growths that have been found in prior tests.
Biopsy
If any suspicious growths are found during a colonoscopy, your doctor will remove a small piece of tissue from the growth. This sample will be sent to the laboratory for further testing.
Can Colorectal cancer be cured?
Early-stage, localised colorectal cancer can generally be cured by removing any cancerous growths in the colon or rectum. However, if the cancer has metastasised and spread to the liver, lungs or other organs, it will be more difficult to treat and may require more than one form of treatment, or an extended treatment period.
Typically, a person’s prognosis will depend on the stage of the cancer, as well as how well each individual responds to various types of treatment.
What are the Treatments for Colorectal Cancer?
There are several types of surgery that may be used to treat colorectal cancer. These include:
- Polypectomy
This refers to the surgical removal of polyps during a colonoscopy. It can be used in some cases of early-stage colorectal cancer.
- Transanal Excision
During a transanal excision, part of the rectal wall is removed. It can be effective in removing early-stage rectal cancers located near the anus.
- Transanal Endoscopic Microsurgery
This procedure is similar to a transanal excision, but makes use of an endoscope to reach growths that are higher up in the rectum.
- Low Anterior Resection
During a low anterior resection, part of the upper rectum is removed. Following this procedure, the colon will be reattached to the remaining part of the rectum.
- Proctectomy
This refers to the total surgical removal of the rectum. After a proctectomy, the colon is connected to the anus in a procedure known as colo-anal anastomosis.
- Colectomy
During a colectomy, all or part of the colon is removed. This may be done through open surgery involving an incision in the abdomen, or with the use of a laparoscope.
- Colostomy
Some patients may require a colostomy after surgery. During this procedure, the colon is cut and sutured to an opening in the skin of the abdomen – also known as a stoma. Colostomies are used to relieve any blockage in the colon and may be temporary or permanent.
Radiation Therapy
Radiation therapymakes use of high-energy rays to destroy cancer cells. It is more commonly used in cases of rectal cancer than colon cancer and is often used in conjunction with surgical treatment or chemotherapy. Radiation therapy can come in two forms: External-beam radiation therapy and internal radiation therapy.
Ablation and Embolisation
Ablation and embolisation may be used to treat colorectal cancer that has metastasised, most often to the liver or lungs.
Ablation is a technique that can be used to destroy small tumours which are less than 4cm in diameter. There are several types of ablation methods available:
- Radiofrequency ablation — This uses high-energy radio waves to destroy cancer cells.
- Microwave ablation — This makes use of electromagnetic microwaves to kill cancer cells in the liver.
- Ethanol ablation — To damage cancer cells, alcohol can also be directly injected into tumours.
- Cryoablation — In cryoablation, a thin metal probe is used to freeze tumours and kill cancer cells.
Embolisation is used in cases of liver tumours, and may take 3 forms:
- Arterial embolisation — In this procedure, small particles are injected into the hepatic artery to reduce blood flow to any tumours in the liver.
- Chemoembolisation — Combining both chemotherapy and arterial embolisation, chemoembolisation is when chemotherapy is delivered to the hepatic artery via a catheter. The artery is then blocked to keep the chemotherapy close to the tumour.
- Radioembolisation — During radioembolisation, microspheres coated with a radioactive substance are injected into the hepatic artery to deliver radiation to any tumours in the liver.
Systemic treatment options, such as chemotherapy, immunotherapy, and targeted therapy, may also be used in cases of colorectal cancer.
Summary
Colorectal cancer is a common type of cancer that is easily treated when detected early. Unfortunately, it does not tend to present itself in visible ways. If you believe that you are at risk of developing colorectal cancer, it is recommended that you attend screenings regularly.
A healthy lifestyle can also help to prevent colorectal cancer, as well as other diseases. You can reduce your risk of developing colorectal cancer by:
- Eating a fibre- and antioxidant-rich diet
- Keeping physically active
- Losing weight
- Reducing alcohol consumption
- Quitting smoking
References
- Singapore Cancer Society, https://www.singaporecancersociety.org.sg/learn-about-cancer/types-of-cancer/colorectal-cancer.html. Accessed 14 October 2022.
- “Colorectal Cancer - Colorectal Cancer – Symptoms, Treatments.” SingHealth, https://www.singhealth.com.sg/patient-care/conditions-treatments/colorectal-colon-cancer. Accessed 14 October 2022.
- “Colorectal Cancer - NCIS.” National University Cancer Institute, Singapore, https://www.ncis.com.sg/Cancer-Information/About-Cancer/Pages/Colorectal-Cancer.aspx. Accessed 14 October 2022.
- “Polypectomy: Definition, Preparation, Procedure & Recovery.” Cleveland Clinic, 8 July 2022, https://my.clevelandclinic.org/health/treatments/23479-polypectomy. Accessed 14 October 2022.
- “What Is Colorectal Cancer? | Colorectal Cancer Research & Statistics.” American Cancer Society, https://www.cancer.org/cancer/colon-rectal-cancer/about.html. Accessed 14 October 2022.
