New blood test may detect cancer at early stage

Scientists have developed a new blood test that can detect cancer and locate where the tumour is growing, providing a potential alternative to invasive surgical procedures like biopsies.
When a tumour starts to take over a part of the body, it competes with normal cells for nutrients and space, killing them off in the process, according to researchers from the University of California, San Diego in the US.
As normal cells die, they release their DNA into the bloodstream and that DNA could identify the affected tissue.
"We made this discovery by accident. Initially, we were taking the conventional approach and just looking for cancer cell signals and trying to find out where they were coming from," said Kun Zhang, a professor at UC San Diego.

"But we were also seeing signals from other cells and realised that if we integrate both sets of signals together, we could actually determine the presence or absence of a tumour, and where the tumour is growing," Zhang added.
Researchers put together a database of the complete CpG methylation patterns of 10 different normal tissues (liver, intestine, colon, lung, brain, kidney, pancreas, spleen, stomach and blood).

They analysed tumour samples and blood samples from cancer patients to put together a database of cancer-specific genetic markers.
Blood samples from individuals with and without tumours were screened. They looked for signals of the cancer markers and the tissue-specific methylation patterns.

The test works like a dual authentication process. The combination of both signals, above a statistical cutoff, is required to assign a positive match, researchers said.
The study was published in the journal Nature Genetics.