Using a new molecular test, investigators at The Johns Hopkins University School of Medicine have detected genetic mutations specific to cancer in blood samples of six patients with head and neck cancer. Their findings are reported in the September issue of Nature Medicine.
"Although quite preliminary, these findings are interesting because the presence of DNA alterations in the blood appears to be associated with large, advanced tumors and with cancer that has spread," said lead author David Sidransky, md, associate professor of otolaryngology/head and neck surgery, and oncology. Sidransky cautioned that the test does not appear to be useful as a screening test for cancer. "But it might be helpful in patient management by identifying patients with a very poor prognosis who may benefit from aggressive therapy," he said.
The test works by identifying replication errors, or chromosomal deletions, in the DNA of cancer cells. In this study, the investigators examined DNA from patients' serum and compared this DNA pattern to normal DNA from circulating white blood cells. They found genetic alterations in the serum of 6 of 21 head and neck cancer patients that were identical to alterations from the tumor itself.
Serum DNA Alterations Linked With Poor Outcomes
Examining disease outcomes, the researchers found that 4 of the 6 patients with positive test results subsequently died of their cancer, as compared with only 3 of 15 with negative test results. The three patients who developed distant metastases were in the positive test group, further indicating that poor outcome may be associated with the presence of serum DNA alterations. These results must be confirmed in much larger clinical trials, Sidransky said.
The technique used in this study was developed by Sidransky's team and was first used to detect cancer cells in urine. The test uses a series of DNA markers to seek out genetic mutations specific to each patient's cancer. "We decided to test serum samples based on evidence from scientists two decades ago which pointed to increased levels of serum DNA in cancer patients," Sidransky said. "More recent studies suggest that cancer cells circulating in the blood may die and release DNA, which is carried through the bloodstream by plasma."
In an accompanying study in Nature Medicine, a team from Switzerland (also coauthors of the Hopkins study) found genetic alterations in the plasma of over 70% of patients with small cell lung cancer. The authors speculate that the higher presence of alterations may be indicative of a high propensity of this cancer to spread.
In addition to Sidransky, other participants in the Hopkins study include Drs. Homaira Nawroz and Wayne Koch from the Department of Otolaryngology-Head and Neck Cancer at Johns Hopkins, and Drs. Philippe Anker and Maurice Stroun from the Laboratory of Plant Biochemistry and Physiology at the University of Geneva in Switzerland.