02 Jan 2010
While his peers grappled with the woes of adolescence like acne and relationship problems, Hashim bin Jeman experienced very different growing-up pains.
As a child, Hashim witnessed his mother – then in her 40s – succumb to stage four colorectal cancer. Subsequently, several of his older siblings struggled with the same painful disease. Two of his elder sisters eventually died from it.
Hashim’s family has a history of familial adenomatous polyposis (FAP), a hereditary disorder that can cause cancer of the large intestine and rectum. FAP occurs because of a mutated gene that causes hundreds or thousands of polyps to grow in the colon.
People with FAP can begin developing polyps in the colon as early as their childhood or teenage years, said Dr Koh Poh Koon, Consultant and Director of Colorectal Cancer Molecular Genetics Research Laboratory, Department of Colorectal Surgery, Singapore General Hospital (SGH).
“By the time they hit their 20s or 30s, their colons will be carpeted with thousands of polyps,” said Dr Koh. The tragic part is, unless the colon is removed, these polyps will become cancerous over time, he added.
Almost 100 per cent of those with FAP risk getting full-blown colorectal cancer before they reach the age of 40.
Like his mother and elder siblings, Hashim carries the mutated gene. His mother passed the gene down to seven of 11 of her children, including Hashim. Children of FAP patients have a 50 percent chance of inheriting the mutated gene from their parents.
Hashim is only 40 years old. If not for colorectal cancer genetic screening and timely intervention, he probably would have succumbed to the disease by now.
Gene testing can save lives
For high-risk cases like Hashim, genetic testing can confirm the diagnosis even before the multiple polyps become obvious or cancerous. FAP is just one example of hereditary colorectal cancers. Hereditary colorectal cancers usually manifest at a much younger age (below 50 years old), in the most productive years of one’s life. People are generally healthy at this age, so most affected individuals tend to ignore any symptoms they may have, seeking treatment only when the disease is at a late stage.
“While we may not be able to control certain environmental factors that may contribute to one’s risk of getting cancer, we can certainly try to pre-empt what you’re born with,” said Dr Koh.
Undergoing gene testing can indicate whether you carry the mutated genes that may cause hereditary colorectal cancer.
According to Dr Koh, colorectal cancer is the most common cancer in Singapore and SGH sees about 60 per cent of all colorectal cancer cases in Singapore. Up to 30 per cent of colorectal cancers may be hereditary, with five to eight per cent of this group being highly susceptible.
Last November, SGH launched the Colorectal Cancer Genomic Health Service, comprising a research laboratory and a Clinical Genetics Service.
With this service, high-risk patients can undergo clinical evaluation to Colorectal Surgery Recovery (CSR) programme find out if they carry genes that greatly increase their risk of colorectal cancer.
The first step includes an interview with a Polyposis Registry Coordinator who evaluates the individual’s family history of colorectal and other cancers to plot a family tree.
Then, the patient is referred to the High-Risk Family Clinic where a doctor will review and determine the types of gene mutations he or she should be screened for.
Before undergoing gene testing, the patient receives genetic counselling from a trained genetic counsellor.
“The counsellor provides a detailed explanation of what the test is about, and what might happen if the test results are positive or negative. You can also ask the genetic counsellor any questions before you decide if you want to proceed with gene testing,” said Dr Koh.
What does a positive result mean?
A positive result indicates a known mutated gene that can lead to hereditary colorectal cancer. Patients with confirmed genetic mutations will receive post-test genetic counselling to explain the diagnosis and the implications of the test results, said Dr Koh.
Their family members will also be counselled and encouraged to go for the same test to determine if they are carriers of the mutated gene. Gene carriers can be offered close clinical surveillance or preemptive surgery as a risk-reduction strategy to prevent the occurrence of cancer.
According to Dr Koh, blood tests are able to detect at least 85 per cent of colorectal cancer gene mutations.
“With hereditary colorectal cancer syndromes like FAP, screening and interventions are important to prevent cancer or early death from the disease,” said Dr Koh. In Hashim’s case, genetic testing has not only saved his life, but those of his family’s too. Hashim and two of his younger siblings, who were screened and diagnosed with FAP, underwent surgery to remove their large intestines and rectums.
Knowing that he has FAP has also changed Hashim’s decision to have more children. He has one teenage son.
“My wife cried when she found out that I had FAP. We were so scared our son would have it too. But thank God his results were negative,” he said.
Click here for jpeg format
« Back to previous
page
back to top