Colon and Rectal Cancer or Colorectal Cancer is the top cancer in Singapore. The number is increasing and has become the commonest cancer in recent years. The lifetime probability of an individual developing colorectal cancer is approximately 1 in 20, and is among the highest in the world. A big proportion of patients are still diagnosed at the advanced stage of the disease. Screening is important because colorectal cancer is a preventable cancer. Most of the cancers of the large intestine are believed to have developed from polyps. Colonoscopy detection and removal of polyps result in a reduced colorectal cancer risk. A polyp removed is a potential cancer prevented.
Screening for colorectal cancer has been proven to save lives. In the United States and Northern European countries, colorectal cancer deaths has been falling, and this has been attributed to screening, early detection and prevention by polypectomy. Read more about Colon and Rectal Cancer
Method of colorectal cancer screening
Stool Occult Blood Test
This stool test checks for minute amount of blood in the stools. This small amount of blood in the stool is usually not visible to the naked eye. If the stool test is positive for blood, colonoscopy is recommended. If the stool test is normal, it needs to be repeated every year.
Barium enema X-ray
Barium enema is a medical procedure used to examine the colon by taking X-ray pictures while barium contrast (which shows up on X-rays) fills the colon. Air may be puffed into the colon to distend it and provide better images. Barium enema has a lower risk of perforation than colonoscopy but still require bowel preparation. There is also a need to perform a colonoscopy if the barium enema is positive for confirmation and biopsy or removal of polyps. Barium enema is not the preferred first line screening choice.
Colonoscopy
Colonoscopy is a specialised investigation where a flexible telescope tube is inserted through the anus to inspect the inner lining of the colon and rectum directly. Biopsies and removal of polyps are possible through the colonoscope. It requires bowel preparation. Colonoscopy is considered the most accurate examination of the colon and rectum. It is a very safe procedure with less than 1 in 1000 risk of complication such as bleeding or perforation. Read more about Colonoscopy
CT Colonography (Virtual Colonoscopy)
CT colonography is a minimally invasive imaging examination of the colon and rectum, using CT scan to acquire images and computer software to process the images for interpretation. It is the best available imaging test if colonoscopy is not suitable for a person, and in this regard superior to barium enema. The main concern over CT colonography is the risk of radiation, which is cumulative, if used repetitively for surveillance. It requires bowel preparation. There is also a need to perform a colonoscopy if the scan is positive for confirmation and biopsy or removal of polyps.
Who should go for colorectal cancer screening?
Average-risk person
Colorectal cancer may occur at any age, although about 90% of the patients are over age 50. The risk increases with age. Average-risk person include individuals who have no relatives with colorectal cancer and have no symptoms at all. For average-risk person, screening should begin at the age of about 50 years.
Increased-risk person
Persons at high risk for colorectal cancer include those who have one or more close relatives (first degree family member) with colorectal cancer. Those with personal history of colorectal polyps or colorectal cancer or breast, endometrial (womb) or ovarian cancer may have a higher than average risk of colorectal cancer. Persons with inflammatory bowel disease are also at high risk of colorectal cancer
Recommendation for colorectal cancer screening
| Risk Group | Screening Method | When to start screening | When to start screening |
|---|---|---|---|
| Average risk | Stool occult blood test | At age of 50 years | Every year |
| Colonoscopy | At age of 50 years | Every 10 years | |
| CT Colonography | At age of 50 years | Every 5 years | |
| Increased risk | |||
| Family history of colorectal cancer before the age of 60 years | Colonoscopy | 10 years before the youngest affected relative at the time of diagnosis or at age 40, whichever is earlier. | Every 5 years |
| Family history of colorectal cancer above the age of 60 years | Colonoscopy | 10 years before the youngest affected relative at the time of diagnosis or at age 50, whichever is earlier. | Every 10 years |
| Personal history of colorectal polyps | Colonoscopy | Every 1 – 3 years after removal of polyps. If result is normal, then colonoscopy should be repeated every 3 – 5 years. | |
| Personal history of colorectal cancer | Colonoscopy | One year after operation | Every 3 years |
| Personal history of ovarian or endometrial cancer. | Colonoscopy | One year after operation |