MBBS (Singapore), M.Med (Surgery)
In Singapore, data from the Cancer Registry showed that colorectal cancer is the most common cancer in males and the second most common cancer in females in the period 2006-2010. In the past five years ending 2010, there were 8,206 cases (up about 4 per cent) compared to 7,909 cases between 2005 and 2009. The age-standardized incidence rates (ASR) for both males and females has climbed consistently over the past three and a half decades since 1971. Amongst the ethnic groups, ASR is highest among the Chinese for both genders. Majority of the colorectal cancer cases are diagnosed at Stage 2 or later.
This increasing incidence in colorectal cancer is postulated to parallel the demographic shift to an ageing population and poor dietary habit, particularly the consumption of red and processed meat, cigarette smoking and alcohol, as well as obesity and physical inactivity. Countries that have had a rapid ‘westernization’ of diet, such as Japan, have seen a rapid increase in the incidence of colorectal cancer. These ‘unhealthy diets’ are postulated to lead to an increase in DNA damage in the colonic cells that causes cancer formation.
Hence environmental factors, such as diet, play a significant role in the development of colorectal cancer. This explains why about 90% of cases were diagnosed at age 50 years or older, reflecting the length of time for exposure to undesirable environmental exposure before colorectal cancer develops. This means that up to 10% of colorectal cancer occur in those who are fairly young, below the age of 50. In those who develop colorectal cancer before 50 years old, genetic factors rather than environmental factors are likely to play a bigger role. It is likely that a young person developing colorectal cancer has a genetic mutation that is inherited from birth, conferring a ‘head start’ in cancer development. An individual who has at least one of the following traits should consider genetic screening for colorectal cancer:
- Strong family history of 3 of more colorectal cancers affecting 2 or more generations
- Strong family history of multiple relatives with cancers in other organs such as the uterus, ovary, small intestine, bladder and kidneys
- Personal or family history of colorectal cancer or polyps diagnosed before 50 years olFamily history with known hereditary conditions:
- Familial Adenomatous Polyposis (FAP)
- Lynch Syndrome
- Puertz-Jegher’s Syndrome (PJS)
- Cowden’s Syndrome
- Multiple polyps in the colon, rectum or the rest of the gastrointestinal tract
- Your managing physician believes there is a possible hereditary component to your colorectal cancer.
A genetic screening is an examination of a person’s genes to look out for patterns of mutations that may indicate a genetic condition or to predict the chance that a person will develop a specific disease or condition in the future. A person found to have an increased risk of certain medical conditions would be better informed about the choices of preventive or therapeutic medical treatments for himself. Having the knowledge can empower a person and his affected family members to make significant life planning decisions that may affect the overall disease outcome, prognosis and the future health status of himself and his family.
Knowing about a certain disease gene may provide vital health/ medical information that could assist your colorectal surgeon in more effectively planning for your clinical care or initiate preventive measures for at-risk individuals. The genetic test is a simple and non-invasive procedure, involving just drawing a small amount of blood from your arm. The blood sample will be sent for thorough lab testing and analysis.