Colon cancer, also known as colorectal cancer, occurs when there is an abnormal proliferation of cells in the epithelium of the large intestine. It mainly develops from colorectal polyps, which can migrate to other organs. According to the 2013 statistical report from the Hong Kong Cancer Registry of the Hospital Authority, colorectal cancer is the second leading cause of death from cancer.
Risk factors of colorectal cancer include:
- Age: risk increases with age, especially for people over the age of 50
- History of colorectal polyps, chronic colitis, breast cancer, or thyroid cancer
- Family history of colorectal cancer
- Regular consumption of high-fat, high-protein, and low-fiber foods or processed meats
- Obesity or being overweight
- Lack of exercise
- Excessive consumption of alcohol
- Bloody or dark stools
- Change in bowel habits (e.g. constipation or diarrhea) lasting more than two weeks
- Mucus in stool
- A feeling that you need to have a bowel movement even after you have just had one
- Weight loss
- Abdominal pain, cramping
- Bowel obstruction which causes vomiting, constipation, and abdominal pain
- Abdominal lumps
Screening and Diagnosis
Early stages of colorectal cancer often show no obvious symptoms. People with a family history of the cancer should undergo a medical check-up every one to two years from 25 years of age onwards. Other high-risk individuals should also undergo regular screening because early detection of colorectal polyps can increase the survival rate and reduce the risk of relapse.
Colorectal cancer screening and diagnosis:
- Colonoscopy (large intestine endoscopy)
- Colon barium enema examination
- Fecal occult blood test (FOBT)
- Blood test – carcinoembryonic antigen (CEA)
- Digital rectal examination (DRE)
Tumour metastasis evaluation and cancer stage determination:
- Computed tomography (CT)
- Virtual colonoscopy
Treatment of colorectal cancer depends on the patient’s condition, which is determined based on the type, size, location, and degree of metastasis of the tumour, as well as the age and physical condition of the patient. Surgery is the main treatment method used for colorectal cancer. Often, adjuvant chemotherapy and/or radiation therapy will be recommended as well.
Surgery involves the removal of the colorectal tumour and surrounding tissues. In the past, laparotomy (i.e. the traditional method) was mainly used. Nowadays, most patients choose to undergo minimally invasive procedures when possible, such as traditional minimally invasive surgery or robotic surgery.
Preoperative (or primary) chemotherapy may be recommended for patients who have tumours that are too large or cancer that has metastasized to other parts of the body. In this case, radiation therapy or chemotherapy is used to shrink the tumour before the surgery, allowing patients to maintain control of their bowel function and avoid the inconvenience of an artificial anus while increasing survival rate.
Chemotherapy is treatment with drugs to destroy cancer cells in an effort to shrink tumours or control their growth.
Targeted therapy employs molecular biology techniques that focus on the mechanisms by which cancer cells mutate, proliferate, and spread in an effort to inhibit their ability to grow and repair.
Radiation therapy is the use of high-energy radiation to kill cancer cells. New systems such as Tomotherapy, a high-speed helical radiation system, direct radiation energy at the tumour, minimizing exposure of energy to normal cells and reducing the development of possible side effects, which may include damage to the small intestine, diarrhea, bloody stool, and poor absorption of food.