Personalised Blood Test for Cancer DNA

A personalised blood test that can identify tumour DNA could be the first step towards a long-promised revolution in the way cancer is treated.

In the short term, the test - reported by Victor Velculescu of Johns Hopkins Kimmel Cancer Center in Baltimore, Maryland, and his colleagues in Science Translational Medicine - could be used to spot cancer recurrence before tumour growth shows up on scans, meaning that treatment could be started earlier.

The test detects genetic rearrangements that distinguish cancer cells from normal cells. Eventually it might also pave the way for more personalised cancer treatments tailored to the genetic signature of individuals' tumours.

Doctors already classify cancers by some of the genes that get switched on by the disease, and use this to guide treatment in some cases. For example, breast cancers are often divided into those that express oestrogen receptors on their surface and are therefore likely to respond to the drug tamoxifen, and those that don't.

Genes have also been identified that predict whether a variety of cancers are resistant to radiotherapy and certain drugs, and might therefore need a different sort of treatment. It is also possible to stratify cancers into aggressive and non-aggressive subtypes according to their genetic make-up.

But that's just the beginning. In the future, pretty much all cancers are likely to be defined by the genetic pathways that drive their growth, rather than where in the body they manifest themselves. And because cancers mutate as they grow, it should be possible to track these changes and tailor patients' therapies accordingly.

Velculescu's test is a step towards this. The real breakthrough will come when such blood tests become sophisticated enough to reveal how tumours are changing over time, rather than simply spotting that they have come back. That should truly revolutionise cancer treatment, enabling the most effective combinations of drugs to be tailored to individual patients - and without the need for painful tissue biopsies.