Blood Test Can Detect Cancer; Here Is How

Stanford scientists have developed a low-cost and highly sensitive blood test that may quickly detect cancer growth and spread.

The test called single colour digital PCR can detect genetic mutations in minute amounts of DNA released from cancer cells into the blood.

The highly sensitive test requires only a fraction of a tube of blood and can detect as few as three mutation-bearing molecules in a single reaction, researchers said. It has the potential to be personalised to recognise mutations unique to any individual cancer, they said.

"For monitoring patient tumours, only a handful of blood tests are available which are limited to only several types of cancers," said Hanlee P Ji, associate professor at Stanford University in the US.

"Nearly all cancer patients require monitoring by whole body imaging, which can be costly, complex, and time- consuming. "In contrast, molecular tests like the one we have developed will enable patients to be monitored at every visit, and thus have the potential for quickly tracking cancer growth and spread," said Hanlee.

The test's rapid turnaround and relatively low cost, especially compared to next-generation DNA sequencing, provide a potential opportunity for universal monitoring of more patients than is currently done, said Hanlee.

Researchers used the test to analyse samples from six patients. Five patients were previously diagnosed with colorectal cancer and one with cholangiocarcinoma or bile duct cancer. After generation of customised mutation detection assays, the researchers were able to identify tumour-derived circulating DNA from three out of six patients.

In one patient, the assay was able to show the presence of three different mutations. The three patients, whose samples did not show elevated cancer DNA, were undergoing active treatment at the time of collection.

The single-colour digital PCR test offers several advantages over other methods of circulating tumour DNA analysis, compared to next-generation targeted sequencing and fluorescent probe-based digital PCR assays. The main advantage is that the new technique does not rely on pre-amplification, which can introduce errors and biases.

"This test is simple enough to set up and analyse without extensive training, and therefore, it can be implemented by anyone, making it highly accessible to any laboratory," said Christina Wood Bouwens from Stanford University.

The research was recently published in the Journal of Molecular Diagnostics.