Dr Ng Lee Beng, Consultant, Dept of Family Medicine & Continuing Care explained that certain tests like cancer markers are not recommended as there is not enough information to support their use.
Many people have the misconception that they need to
do cancer or tumour marker tests to screen for cancer.
A blood-cancer marker is a substance produced in
the body by cancerous cells. It is also made by some
normal cells, although the levels tend to be much
higher when there is cancer.
However, such tests are generally considered to be of
Dr Ng Lee Beng, a consultant at the Singapore General Hospital's family medicine and continuing care department,
said cancer markers are not sensitive as they
do not pick up cancer most of the time. Also, a positive
result does not usually mean that a person has cancer,
Dr Lim Siew Eng, a senior consultant at the haematology-
oncology department at the National University
Cancer Institute, Singapore, said blood tests should
preferably not be used in place of recommended
screening tests for cancer.
“Blood tests are convenient. But they have not been
shown to reduce cancer mortality and may not detect
cancer earlier, and could also give rise to a false sense
Instead, Dr Lim advises people to do recommended
age-specific tests – mammography for breast cancer,
Pap smears for cervical cancer, and stool blood tests or
colonoscopy for colon cancer. These tests should be
done even if one does not have a family history of the
Dr Winston Ho, the medical director of Parkway
Shenton, said that if cancer markers are used and
cancer is suspected, other tests such as scans, scopes or
biopsies are needed to confirm the diagnosis.
Non-cancerous conditions can also give rise to an
elevated cancer marker, he added.
For instance, a rise in cancer antigen 125 or CA125
levels, an indicator of ovarian cancer, may be caused by
endometriosis, and the CEA (carcinoembryonic antigen)
indicator for colon cancer may be elevated due to
inflammatory bowel disease.
But though there are limitations to using blood
cancer markers as a general screening tool, they are
non-invasive and more affordable, Dr Ho said.
He said cancer markers are most useful when used to
monitor response to cancer treatment and to screen
They are also useful for older people or at-risk
persons with predisposed conditions, he added. For
instance, hepatitis B carriers are advised to check their
liver-cancer marker every six months as this liver
infection is the major cause of liver cancer.