Gene test can identify bits of cancer in blood

CHICAGO (Reuters) - A personalized blood test can tell whether a patient’s cancer has spread or come back, offering a better way to see if treatments are working, U.S. researchers said on Thursday.

Having a test that can detect tumors in the blood could help doctors customize cancer treatments, offering more aggressive therapy to some patients while sparing others from unneeded chemotherapy or radiation.

“We’re talking about what could be a management tool for a number of patients,” said Dr Bert Vogelstein of Johns Hopkins University in Baltimore and the Howard Hughes Medical Institute, who worked on the study published in the journal Science Translational Medicine.

The gene-based test takes advantage of rapid advances in the technology to sequence whole genomes -- all of a person’s genetic code -- once a very costly and time-consuming task.

“This is really personalized medicine. This is not something off the shelf,” Vogelstein said in a telephone interview. “This is something that has to be designed for each individual patient.”

For the study, the researchers took six sets of normal and cancerous tissue from four colorectal and two breast cancer patients, and mapped out the genetic code in each.

In the cancer samples, the team looked for areas in the genetic code where there were extra DNA copies, or where sections of chromosomes had fused together.

“There are about nine or so rearrangements on average in every sample,” Dr Victor Velculescu of Johns Hopkins told reporters at the American Association for the Advancement of Science meeting in San Diego. “They are not present in the normal tissue.”

Once the team had identified a genetic signature of the tumor, they looked in patients’ blood to see if they could find remnants of DNA that had been shed from the tumor.

They found it in two patients with colorectal cancer.

After these patients had surgery to remove their tumors, levels of the tumors’ genetic signature or biomarker, fell, but later returned, suggesting that the cancer remained in the patients’ bodies. After a second surgery and a round of chemotherapy, the cancer biomarker levels fell again.

The team thinks the blood tests could be used in cancer patients to detect tumors before they grow big enough to be spotted on imaging machines.

Right now, the test is too costly to be practical.

“It costs right now about $5,000 to do it,” Vogelstein said. “There is no question in a couple of years that cost will come down by tenfold at least. Then, a test like this will cost less than an MRI or CT scan,” he said.

Velculescu said the test could be available to a broad number of patients in as few as two years.

Meanwhile, the team plans to keep refining the technology and has filed for patents for the blood test.

Editing by Eric Beech