Cancer Detected Using Blood Test and Gene Sequencing
12 Dec 2012
A test that combines the ability to detect cancer DNA in blood with genome sequencing technology could be used to screen for cancers, monitor cancer patients for recurrence, and find residual cancer left after surgery.
To develop the test, scientists at the Johns Hopkins Kimmel Cancer Center (Baltimore, MD, USA; www.hopkinskimmelcancercenter.org) took blood samples from late-stage colorectal and breast cancer patients and healthy individuals, and looked for DNA that had been shed into the blood. Whole-genome sequencing technology was applied to DNA found in blood samples, allowing the investigators to compare sequences from cancer patients with those from healthy people. The scientists then looked for telltale signs of cancer in the DNA: dramatic rearrangements of the chromosomes or changes in chromosome number that occur only in cancer cells.
No signs of cancer-specific chromosome changes were found in the blood of healthy individuals, but the investigators found various cancer-specific alterations in the blood of all seven patients with colon cancer and three patients with breast cancer. Using specialized bioinformatic approaches, they were able to detect these alterations in a small fraction of the millions of DNA sequences contained in the blood sample.
"This approach uses the power of genome sequencing to detect circulating tumor DNA in the blood, providing a sensitive method that can be used to detect and monitor cancers," said Victor Velculescu, MD, PhD, professor of oncology and codirector of the Cancer Biology Program at Johns Hopkins.
A report describing the new approach appears in the November 28, 2012, issue of the journalScience Translational Medicine.
Prof. Velculescu said that additional research will focus on determining how the new test could help doctors make decisions on treating patients. For example, the blood test could identify certain chromosomal changes that guide physicians to prescribe certain anticancer drugs or decide patient enrollment in clinical trials for drugs that target specific gene defects. Currently, physicians use cellular material biopsied from the original tumor to make these decisions, but tumor material can often be inaccessible or unavailable.