New York City ? Blood tests derived from the DNA of cancer patients’ tumors will offer doctors a new way to determine whether the patients’ treatment has eliminated the disease, a study said.

Scientists at the Johns Hopkins Kimmel Cancer Center and Life Technologies, a Carlsbad, Calif.-based biotechnology company, scanned the genomes of six cancer patients, looking for large chunks of rearranged DNA. These alterations occur in cancer cells but not in healthy tissue. By using these gene sequences to create biomarkers, or “red flags,”the researchers were able to see whether the patients’ blood, tested after treatment, contained any traces of DNA from the tumor.

These blood tests may give oncologists a clearer picture of how a patient is responding to treatment, according to a report published online in the journal Science Translational Medicine. The blood tests may alert doctors to a recurrence of cancer earlier than commonly used imaging tools, such as CT scans, would detect it.