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Colorectal Cancer Overview


Colorectal cancer is the most common cancer and second leading cause of cancer deaths in Hong Kong. According to the latest statistics from Hong Kong Cancer Registry, there were 5,437 new cases of colorectal cancer in 2016, with 2,089 deaths caused by colorectal cancer[1]. Unlike most of the high-risk cancers, colorectal cancer can be prevented by regular colorectal cancer screening. Jointly issued by the U.S. Preventive Services Task Force which represents the American College of Gastroenterology, the American Gastroenterological Association and the American Society for Gastrointestinal Endoscopy, colorectal cancer screening recommendations[2] outline that people at average risk of colorectal cancer should initiate a routine for colorectal cancer screening from the age of 50. Early detection and removal of precancerous lesions has been proven to significantly reduce the risk of developing colorectal cancer[3].


For most colorectal cancers, surgical resection is the primary and most effective treatment. Below is the latest information about colorectal cancer treatment and an overview of the options, including colorectal cancer screening, diagnosis and treatment, plus FAQs.

Symptoms and Signs of Colorectal Cancer

  • A persistent change in bowel habits (such as constipation or diarrhea)
  • Abdominal discomfort
  • Constant fatigue or weakness
  • Dark stools or blood in the stool
  • Iron deficiency
  • Bleeding from the colon/rectum
  • Weight loss

What Is Colorectal Cancer?


The intestine is made of 2 parts, the small intestine and large intestine. Colon and rectum are parts of the large intestine and therefore, colon cancer and rectal cancer are also known as colorectal cancer. Colorectal cancer begin when polyps on the inner surface of the large intestine become cancerous, removing these polyps (before cancerous) through surgery can help reduce the risk of developing colorectal cancer[4]. Symptoms may include chronic constipation and diarrhoea, blood on or in the stool and unexplained weight loss. Unfortunately, not everyone experiences symptoms during the early stages of this cancer; it is vital to have regular screenings to help prevent advancing into incurable stages.


Please consult your doctor should the following colorectal cancer symptoms persist

Colorectal Cancer Causes and Risk Factors


There are a number of risk factors that might increase a person’s chance of developing colorectal cancer for example, an unhealthy lifestyle and diet which have led it becoming more and more common and to an increase in colorectal cancer in younger adults.


The following are a list of factors that may influence the risk of developing colorectal cancer:

  • A family history of colorectal cancer*
  • Colorectal polyps
  • Being older – 90% of colorectal cancer patients are over 50[5]
  • Certain types of diets – a diet that has insufficient fibre or high in red meat, processed meat and fats, all of which raise colorectal cancer risk
  • An unhealthy life style – smoking, drinking and a lack of fitness
  • Inflammatory bowel disease – such as ulcerative colitis and Crohn’s disease
  • A previous history of colorectal polyps or colorectal cancer

*Some family cancer syndromes will significantly increase the risk of colorectal cancer, including:

  • Familial adenomatous polyposis (FAP): the likelihood of patients with FAP developing colorectal cancer before the age of 50 can be as high as 93%[6]
  • Lynch syndrome (hereditary non-polyposis colon cancer or HNPCC): approximately 80% of patients with HNPCC will develop colorectal cancer before the age of 70[7]

Colorectal Cancer Screening Options


Fecal Occult Blood Tests (immunohistochemical test)

Recommended for anyone devoid of colorectal cancer symptoms as an initial screening option. The test examines for occult (hidden) blood in the stool by collecting a small stool sample[[8].


Computed Tomographic Colonography (CT)

Is a less invasive screening option that uses a CT scanner to produce a series of pictures of the colon and rectum from outside the body. Should polyps or other abnormal growths be discovered during CT, patients will need to undergo a standard colonoscopy for a thorough assessment.


Standard (or optical) colonoscopy

People at high risk of colorectal cancer or with suspicious polyps or other abnormal growths identified during an initial screening are recommended to undergo a standard colonoscopy. In this examination, the inner lining of large intestine (rectum and colon) is examined using a colonoscope – a thin and flexible tube with a lens for viewing. The colonoscope is inserted through the anus and advanced to the other end of the large intestine. During a colonoscopy, the physician can remove any abnormal growths in the colon and the rectum whilst collecting tissue samples for a more detailed analysis.



Sigmoidoscopy is like colonoscopy and, is a procedure that uses a thin and flexible tube with a lens. Sigmoidoscopy covers only the lower part of the colon, examining the rectum and sigmoid colon. Since a sigmoidoscopy only looks at part of the colon covering just 50% of the area, the associated risk is relatively low as a medical procedure.

People at high risk of developing colorectal cancer should consult their doctors and consider starting screening at an earlier age (for example, 40, compared with an average risk of 50).

Colorectal Cancer Treatment

Before deciding on a colorectal cancer treatment option, patients are required to perform a full body check-up, including Magnetic Resonance Imaging (MRI) and Positron Emission Tomography/Computed Tomography (PET-CT), for a thorough analysis of their cancer stage. The following are the latest colorectal cancer treatment options:

1. Traditional Colorectal Cancer Surgery

Once patients are diagnosed with colorectal cancer, surgical resection is the most effective treatment. Doctors will perform a minimally invasive surgical resection to remove the identified cancerous tissue and surrounding tissue, and then examine whether the cancer cells have metastasised to the lymph nodes. Normally, patients will recover in a short period of time without it seriously disrupting their daily lives. Take colon cancer for example, the surgery usually only requires the resecting of a small portion of the intestines. And the ends of the intestines can be reconnected without significantly affecting digestive functioning.


However, if the surgery involves the removal of anus and rectum, patients may need to undertake additional surgeries such as colostomy or ileostomy which create a permanent or temporary stoma in the body, an artificial opening that allows waste (faeces or urine) to be diverted out of the body. Currently stoma care is very advanced; they can be firmly attached to the skin and are available with deodorizer to ensure the minimum inconvenience for swimming and when doing other sports. However, given that having a stoma care product can take a drastic psychological toll on the patients, it should be avoided unless absolutely necessary.

2. Transanal Total Mesorectal Excision (TaTME)

This procedure removes rectal cancer using an instrument inserted into the anus. This surgical technique is still in its developmental stage and requires more clinical evidence to determine its full potential. However, it has been gaining popularity worldwide and has already been adopted in Hong Kong as a colorectal cancer treatment.

3. “Watch-and-Wait” Approach

In individual cases that involve the tumour in the lower parts of the intestines, which is 5 cm or less from the anus. Traditional colorectal cancer surgeries normally remove the anus and sphincter, creating in the body a permanent or temporary artificial opening to where the flow of waste will be discharged. The “Watch-and-Wait” treatment approach, on the other hand, applies chemotherapy and radiotherapy before the operation and aims to reduce the size of the tumour, delay and even avoid surgery, so that the patients may continue to discharge digestive waste materials from their body normally.


In the first year of treatment, patients are required to undertake at least seven MRIs. After that, patients will also need to receive MRI screenings and colonoscopy on a regular basis so medical staff can closely monitor their recovery. With approximately 30% of these patients being reported to have their cancerous cells completely vanish when using this approach, there is still a risk of recurrence (around 50%). Fortunately, 90% of patients who suffer recurrence can still be cured via radical colorectal resection.

4. Targeted therapy for late-stage colorectal cancer

In the past, there were limited treatment options for late-stage colorectal cancer. Thanks to medical advancement, there are now more new ways than ever to treat patients with late-stage colorectal cancer, allowing them to live longer than the three year survival average. Doctors will advise on treatment plans based on the patient’s health. First-line targeted therapy tends to involve chemotherapy as a combined treatment option. If the first-line treatment gradually becomes ineffective, there are other options such as combining second-line, third-line and even fourth-line treatments. Adopting immunotherapy can also be a good treatment option.


Current targeted therapy suited to late-stage colorectal cancer are generally classified as Anti-Vascular Endothelial Growth Factor (VEGF) and Epidermal Growth Factor Receptor (EGFR). EGFR is usually used to treat patients who do not have mutations in the KRAS gene.

Frequently Asked Questions About Colorectal Cancer

  • Q1.When Should I Begin to Get Screened?

    As colorectal cancer symptoms may be minor or non-existent during the early stages of the disease, it is recommended to begin screening for colorectal cancer soon after turning 50 to effectively reduce your risk of developing colorectal cancer, even if you have never observed any colorectal cancer symptoms in the past. According to research conducted by the American Cancer Society, more young adults are getting colorectal cancer nowadays and therefore, people most at average risk of colorectal cancer are recommended to start their regular screening at the age of 45 [9].


    In addition, under the recommendations by Hong Kong’s Cancer Expert Working Group on Cancer Prevention and Screening (CEWG), Department of Health urges citizens aged over 50 to take a faecal occult blood test once every year or two; or sigmoidoscopy once every five years; or standard colonoscopy once every 10 years. High-risk individuals such as those with a family history of colorectal cancer should visit their doctor to get screened at an earlier age[10].

  • Q2.What are the stages of colorectal cancer?

    Similar to most cancers, colorectal cancer is generally classified into one of 4 stages, depending on the size of the tumour, how far the cancer has metastasised in the body and the progression of the disease. There are individual cases to which the staging system cannot be applied. For more information, please refer to cancer staging system.

  • Q3. Is surgery the only proven treatment for colorectal cancer?

    Before cancerous cells spread to other organs, surgery is usually recommended as the primary treatment for colorectal cancer. However, patients can also consider other treatment options such as combining chemotherapy with the “Watch-and-Wait” approach, immunotherapy and targeted therapy. Approximately 30% of patients with colorectal cancer who were treated with the “Watch-and-Wait” approach have found their cancerous cells disappeared completely.


    In addition, for patients with stage IV colorectal cancer, a treatment plan that combines chemotherapy and targeted therapy is highly regarded as most suitable, because it not only alleviates the patient’s symptoms, but also improves their quality of life. Specific treatment plans can only be determined by the nature of the tumour (such as hereditary), the age and health conditions of the patient and other health-related issues.

  • Q4. Is chemotherapy compulsory after colorectal cancer surgery?

    Patients with early-stage colorectal cancer generally are not required to undergo chemotherapy after surgery. However for patients with late-stage cancers, such as stage II and III, it is likely that cancer cells still remain in the body after surgery therefore chemotherapy is highly recommended to help prevent recurrence.


    Chemotherapy treatment normally lasts for three months to a year. Mainly targeted at patients with rectal cancer, radiotherapy is given five times a week for a total of six weeks. Some of the latest radiotherapy technologies such as Tomotherapy can reduce the side effects remarkably, by adjusting the size, shape and intensity of the radiation beam to accurately target the size, shape and location of the patient’s tumour and minimize the damage to surrounding tissue.


    In addition, for patients with stage II and III rectal cancer, treatment plans that combine chemotherapy and radiotherapy, known as chemoradiotherapy is recommended prior to the surgery. Not only can it reduce the size of the tumour and the risk of recurrence, but it also reduces the likelihood of the patient requiring a permanent stoma after the surgery.


    Before the surgery, one of the treatment options is to combine chemotherapy with the “Watch-and-Wait” approach using MRI and colonoscopy. This method monitors the development of the disease, delays and even avoids the application of a surgical procedure. For patients who are younger or whose tumour is located closer to the anus, this combined treatment method can avoid the complete removal of the anus and sphincter and the creation of a stoma, allowing them to discharge waste as they normally would and thus greatly improves their quality of life.

  • Q5. What is the follow-up care after surgery?

    When the sedative wears off, movements of the intestine generally slows down. Patients are recommended to start drinking a small amount of water after two to three days of the surgery and gradually increase the amount of water intake. After four to five days, patients can start taking a light diet as directed by their medical professionals[11].


    In addition, after the removal of tumour, some patients may need to undertake a colostomy or ileostomy. They need to learn how to examine, clean and change the stoma bag. It is important that their family, friends, and counsellors are understanding and offer them their full support during this transition.

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  1. http://www3.ha.org.hk/cancereg/pdf/factsheet/2016/colorectum_2016.pdf
  2. https://www.asge.org/docs/default-source/education/practice_guidelines/piis0016510717318059.pdf?sfvrsn=0
  3. https://www.chp.gov.hk/files/pdf/colorectal_ca_tc.pdf
  4. https://www.cancer-fund.org/colorectal/early-detection-reducing-risk/?gclid=EAIaIQobChMIhILj38XN4QIVSGoqCh3FJA0dEAAYASAAEgKOLPD_BwE
  5. https://www.chp.gov.hk/files/pdf/colorectal_ca_tc.pdf
  6. http://www.patho.hku.hk/dept/services/colonreg-faptc.htm
  7. http://www.patho.hku.hk/dept/services/colonreg-hnpcctc.htm
  8. https://www.colonscreen.gov.hk/mobile/tc/public/about_crc/common_tests_for_crc_screening.html
  9. https://www.cancer.org/latest-news/american-cancer-society-updates-colorectal-cancer-screening-guideline.html
  10. https://www.colonscreen.gov.hk/tc/public/programme/understand_the_suitability_for_receiving_crc_screening.html
  11. https://www.cancer-fund.org/wp-content/uploads/2017/07/%E5%A4%A7%E8%85%B8%E7%99%8C.pdf