DNA tests for cancer promised

A personalised blood test that could track how a tumour responds to treatment and whether cancer is recurring has been developed by researchers in the U.S. The team from the Johns Hopkins Kimmel Cancer Centre presented their findings at the American Association for the Advancement of Science's annual meeting in California.

The researchers analysed normal and cancerous tissue from four colorectal and two breast cancer patients, during their study. They were looking for rearrangements of large chunks of DNA, which typically occurs in cancerous but not normal cells. Previous research has focused on single letter DNA changes. Between four and fifteen DNA rearrangements were found in each of the six samples.

Victor Velculescu, senior author and associate professor of oncology at John Hopkins said: 'Every cancer analysed had these rearrangements and every rearrangement was unique and occurred in a different location of genome....No two patients had the same exact rearrangements and the rearrangements occurred only in tumour samples, not in normal tissue '.

Using the new method, which has been named Personalised Analysis of Rearranged Ends (PARE), the researchers were able to develop biomarkers specific to each patient. When the researchers tried the blood tests on two of the colorectal cancer patients, they found the markers were sensitive enough to detect tumour DNA that had been shed into the bloodstream.

The biomarkers therefore offer a reliable measure that would be useful for monitoring how the tumour reacts to specific therapies. It could also detect recurrent cancers before they are found by conventional imaging methods. Eventually, the approach could pave the way for treatments tailored to the genetic signature of a patient's tumour.

'There is currently no test for cancer patients that provides personalised biomarkers for clinical management of disease, and we feel that this is an important step in bringing new genome sequencing technologies to personalised patient care', said Professor Velculescu.

One drawback of the test is the expense of sequencing, which costs around £3200 per patient, but the researchers say costs are falling as the technology improves. They believe the PARE test will eventually be more cost effective than standard hospital CT (Computerised (Axial) Tomography) scans, which are less sensitive to microscopic cancers.