Immediate family members of people who have colorectal cancer have a higher risk of developing the cancer than the general public.
But a new Singapore study has found that they are not aware of the heightened risk or that they should undergo screening earlier.
These first-degree relatives - such as children, siblings and parents - were also unaware that they should have a colonoscopy to screen for the cancer, and not the more common faecal occult blood test.
Dr Tan Ker Kan, the study's lead author, who is a consultant in the division of surgical oncology (colorectal surgery) at the National University Cancer Institute, Singapore (NCIS), said: "Our findings showed that 100 per cent of the first-degree relatives and patients had not undergone colonoscopy and were not aware that it is an accurate test for colorectal cancer.
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"They tend to mix up the basic screening packages and assume that such packages include screening for the risk of colorectal cancer."
The faecal occult blood test is used to detect tiny amounts of blood in the stool that could be a sign of cancer or polyps.
First-degree relatives of patients should go for a colonoscopy at 50 years of age or 10 years prior to the case involving the youngest patient in the family, whichever is earlier. This means that if the patient is 50 years old, the first-degree relative should get screened from the age of 40.
"If these (tiny amounts of blood in the stool) are found, a colonos- copy will be done to determine the cause of the occult blood. Cancer is found only about 5 to 10 per cent of the time," said Dr Tan.
In a colonoscopy, a long, thin, flexible and lighted tube is inserted through the anus, and into the rectum and colon to check for polyps or cancer inside the rectum and the entire colon.
During the test, if polyps are found and deemed safe to be removed, the surgeon would proceed to remove them to prevent them from developing into cancer.
In most instances where cancer is found, the surgeon would remove the cancer tumour with the surrounding colon, said Dr Tan. This also applies to polyps that are too big to be removed safely.
The study also showed that first- degree relatives were not counselled by doctors on their higher risk of developing the cancer, as well as the need for more stringent screening procedures.
Furthermore, these first-degree relatives may not want to go for colonoscopy due to fear of the procedure and the perception that it is costly, as well as the thought of its inconvenience.
They also felt that they were still young and asymptomatic, and they could thus delay the screening.
A colonoscopy can cost about $1,100 to $2,500 at public hospitals, but patients do get a subsidy. At National University Hospital, the cost for subsidised patients can range from about $300 to $615 and at Singapore General Hospital, it costs about $580 to $830.
The study's 50 colorectal cancer patients and 31 first-degree relatives were recruited between June and December 2015. This is the first time such a study has been done here and in Asia, focusing on the barriers of screening among first-degree relatives, said Dr Tan.
In Singapore, colorectal cancer is the most common cancer for men and the second most common cancer for women.
Every day, five people here are diagnosed with colorectal cancer and two die of it.
Studies elsewhere have shown that about 10 per cent of first- degree relatives end up getting cancer if they are not screened.
In Singapore, the five-year survival rate for colorectal cancer patients ranged from 9.2 per cent in patients with Stage IV colorectal cancer (where the cancer had spread) to 84.3 per cent in patients with Stage I colorectal cancer.
First-degree relatives of patients should go for a colonoscopy at 50 years of age or 10 years prior to the case involving the youngest patient in the family, whichever is earlier, advised Dr Tan.
This means that if the patient is 50 years old, the first-degree relative should get screened from the age of 40.
Those without a family history can get screened from the age of 50 and they can opt for a faecal occult blood test, which should be repeated yearly if the results are negative.