Cheap blood test to revolutionise cancer care

Cancer diagnosis and treatment could be “revolutionised” by a new low-cost blood test that allows doctors to track genetic changes in tumour cells, it was claimed today.

The “liquid biopsy” test identifies defective fragments of DNA shed into the bloodstream by cancer cells as they die.

Scientists have already used it to detect genetic faults involved in tumour growth in blood samples from 20 women with ovarian cancer. They were also able to build a “real time” picture of how one woman’s breast cancer responded to treatment over more than a year.

Study leader Dr Nitzan Rosenfield, from Cancer Research UK’s Cambridge Research Institute, said: “This type of blood test has the potential to revolutionise the way we diagnose and treat cancer. The great advantage is that it can be used to identify cancer mutations without surgery or a biopsy, making it safer and cheaper.”

In future, patients could be given treatments based on the result of a quick blood test, rather than having a tissue sample surgically removed for analysis.

The test is said to overcome a major drawback of tumour biopsies, which may provide only a limited snapshot of the genetic mutations present in cancer.

Once a disease has spread, it is also difficult to take samples from secondary tumour sites throughout the body.

Because DNA is shed from all tumours into the bloodstream, the test provides a bigger picture of the cancer’s progress.

It is the first time scientists have been able to screen entire genes in a blood test to identify cancer mutations, say the researchers, whose work appears in the journal Science Translational Medicine.

Using a DNA-mapping technique called “tagged amplicon deep-sequencing” (TAm-seq), the scientists looked for cancer mutations in blood samples from women with advanced ovarian cancer.

A search for 20,000 possible mutations in six cancer-linked genes revealed rare molecules containing specific genetic faults. In one ovarian sample studied, the test detected a new genetic defect not spotted in the original biopsy. The mutation was only present in a small number of cells in one part of the tumour, and could not be identified in most areas tested.

DNA was also monitored in blood samples taken from several ovarian and breast cancer patients.

In one breast cancer patient, ten mutations were tracked over 16 months.

Study author Dr James Brenton, a Cancer Research UK ovarian cancer clinician, said: “Our technique is much more comprehensive and practical than others that have been used to measure DNA in the blood.

“This tumour-specific DNA offers us an opportunity to follow the disease in ‘real-time’ as it changes, helping us to respond and change the treatments we use against the disease.”