Biomarkers for five cancers found in blood

Scientists in the United States have identified a DNA "signature" in blood that indicates the presence of five different cancers and could mark a breakthrough in diagnosis of the disease.

It could mean being able to screen for bladder, breast, colon, pancreatic and prostate cancers with just a blood test.

Breast, colon and prostate are among the most common cancers in Singapore while bladder and pancreatic cancers are difficult to detect.

While some local experts hailed the discovery, at least one has also raised concern that the test might be overly sensitive and could cause unnecessary anxiety.

The discovery by researchers at the National Human Genome Research Institute (NHGRI) in the US was published in the Journal of Molecular Diagnostics this month.

The researchers found that the five cancers result in 1 per cent to 10 per cent of DNA in the blood being tumour DNA.

Dr Laura Elnitski, a senior investigator at NHGRI, said the next step is to get blood samples from people with such cancers to determine the accuracy of cancer detection when there are low levels of tumour DNA.

The team also found evidence that such "signatures" exist for many more types of cancers, some of which are difficult to diagnose at early stages.

Professor Kanaga Sabapathy, head of cellular and molecular research at the National Cancer Centre Singapore, called it "an astounding discovery" that could have a huge impact on how cancer screening is done in the future.

He said: "There are currently no biomarkers that can reliably detect the presence of cancers in unsuspected individuals, and cancer screenings are not yet able to cover the full cancer spectrum in entirety.

"With such a huge gap in cancer detection, this study brings us closer in the dream pursuit of non-invasive tests that can be used for the detection of multiple cancers in a healthy individual, using a simple blood test."

Professor Chng Wee Joo, director of the National University Cancer Institute Singapore, agreed that it is "potentially useful" but he has concerns.

As the test does not specify exactly what type of cancer is detected, a positive result will lead doctors to search the whole body for cancer.

It is worse if the blood test is more sensitive than existing cancer-detecting imaging tools such as the PET-CT (positron emission tomography - computed tomography).

"There is a risk that if this test is very sensitive, it will detect tumours that are not detected by PET-CT."

He added: "There is a risk with this highly sensitive new test that when it is positive, we are unable to proceed, leading to patient anxiety.

"You still have to wait till you have a detectable tumour before you can do a biopsy to confirm the tumour type and start treatment."

Prof Chng said it could be worse if there is a high rate of false positives, which means the test indicates cancer when the disease is not present.

Both cancer experts agree that it will take several years of work before such a blood test is available for use.

salma@sph.com.sg

Get MyPaper for more stories.