Colon Cancer Screening

Colon cancer is the commonest cancer in Singapore and also in many parts of the developed world. In Singapore, one in twenty persons have a chance of developing colon cancer in their life-time. Statistics from the World Health Organization show that there is a 50-fold difference between the highest (New Zealand) and lowest risk (Bangladesh) countries. The risk within the same race in different countries is also different. This indicates there are genetic and environmental factors that affect risk. Hence, increasing the “protective” factors and reducing the “risk” factors during our life-time from a young age can potentially help to reduce the risk of colon cancer.

What are the factors linked with colon cancer?

“Protective factors”

• High fibre diet
• Increased vegetables and fruit intake
• White meat: fish and chicken
• Calcium, selenium and folate
• Aspirin and estrogen

"Risk factors”

• High saturated fats
• High calories
• Red meats
• Low fibre
• Sedentary life-style
• Obesity

During our life-time, environmental factors act to damage genes and create mutations. These mutations accumulate in the colon and result in the development of polyps that eventually grow to become cancer. This process takes many years and hence colon cancer starts to appear around 45-50 years of age in the person with an “average” risk. In persons with “increased” risk, mutated genes are inherited from parents and this accelerates the pace of cancer development, occurring as young as 20-30 years of age. Therefore, screening for colon cancer is recommended at age 45-50 years for the person at “average” risk, i.e. without a family history of colon cancer. In persons at “increased” risk, i.e. with one or more immediate family members with cancer or polyps, screening is started at an earlier age.

When and how to screen for colon cancer?

“Average Risk”

• Start at 45-50 years
• Colonoscopy every 10 years
• Stool occult blood every year

“Increased risk” with a family history of cancer or polyp

• Start at 10 years earlier than the affected relative
• Colonoscopy

Screening is the use of a medical test to detect disease in persons without symptoms. Persons with polyps and early colon cancer do not exhibit any symptoms. Cancer in the early stages (1 and 2) can be treated by surgery with >80% chance of cure. If we wait until symptoms occur (bleeding, change in bowel pattern), cancer may be at an advanced stage (3 and 4) and the chance of cure falls significantly. About 50% of colon cancers in Singapore are still diagnosed at an advanced stage. Hopefully, this situation can be improved as more people turn to screening. Colonoscopy is the most accurate screening test for colon cancer. It is superior to stool tests and also detects polyps. Polyps can be completely removed, thereby preventing the development of cancer.

About the author. Dr Yap Chin Kong, is a leading Specialist and Senior Consultant in Gastroenterology, Liver Diseases and Endoscopy. He was awarded a Merit Scholarship to study Medicine at the National University of Singapore and graduated with a Bachelor of Medicine & Bachelor of Surgery degree in 1983. In 1988 he obtained his Masters degree in Medicine (Singapore) and became a Member of the Royal College of Physicians (United Kingdom). He became a Fellow of the Academy of Medicine (Singapore) in 1994 and a Fellow of the Royal College of Physicians (Edinburgh) in 2000. In 1992, he was awarded the Health Manpower Development Program Award by the Ministry of Health to pursue advanced training in therapeutic ERCP (Endoscopic Retrograde Cholangio-Pancreatography) at the Academic Medical Centre in Amsterdam, The Netherlands. After a year of extensive experience he returned in 1993 to develop endoscopy further at the Singapore General Hospital until he left for private practice in 2004. He pioneered the use of endoscopic ltrasonography at SGH for a decade. During this time, he taught many generations of medical students and post-graduate doctors. In 2002, he continued to pursue his interest in early cancers of the stomach and colon and visited the Showa University Hospital in Yokohama, and the National Cancer Centre in Tsukiji, Tokyo. He lectured and taught at workshops locally and internationally, combining the best of Western and Eastern techniques. A Master endoscopist, he developed an innovative cap-fitted gastroscopy technique that is used to help countless patients worldwide. He was President of the Gastroenterological Society of Singapore (1999 to 2003) and was President of the Asia-Pacific Digestive Week in 2003. He is currently in private practice at Mount Elizabeth Medical Centre. His broad specialist experience include advanced endoscopy techniques such as ERCP treatment of bile duct stones and pancreas diseases, endoscopic ultrasound, treatment of esophagus, stomach, colon and liver cancers, viral hepatitis and inflammatory bowel disease. He is Visiting Consultant to the National University Hospital and Kandang Kerbau Womens’ & Childrens’ Hospital where he supervises gastroenterologists-in-training and performs endoscopy for sick children.