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DNA Blood Testing May Be an Alternative to Tumor Sampling for Identifying EGFR Mutations

Circulating cancer DNA in the blood of cancer patients appears to be able to provide information similar to that obtained from tumor tissue sampling, according to a study presented at the European Lung Cancer Conference. This makes blood testing for DNA an attractive option in cases where tumor tissue is not available.

These results have important implications for selection of targeted therapies aimed at specific cancer mutations, said presenting author Martin Reck, MD, Department of Thoracic Oncology at Lung Clinic Grosshansdorf, Germany.

There are circumstances where it is difficult, if not impossible, to obtain tumor tissue for genetic testing, he explained, and studies suggest that DNA from the tumor that circulates in the bloodstream can identify mutations present in the tumor. To test this assumption, the large international ASSESS trial compared the ability of blood testing versus standard tumor tissue testing to detect EGFR mutations.

“We were really asking a question on behalf of patients. Is there a valid test that can identify an EGFR mutation and give me the opportunity for superior treatment, even if my lung tumor is not accessible for bronchoscopy or CT-guided biopsy? And, are the results of this blood test in agreement with the results of the ‘gold-standard’ tissue test?” Reck stated in a press release from the European Society of Medical Oncology.

The investigators assessed 1162 matched tumor tissue and blood samples for the presence of an EGFR mutation in lung cancer patients. An 89% agreement was found between the 2 types of tests. Plasma testing identified about half of the patients with EGFR mutations compared with tumor tissue sampling, for a sensitivity of 46%.

Reck pointed out that the tests in this study were performed in local labs used in routine clinical practice, not in a centralized lab selected for a clinical trial. This makes the results more reflective of the “clinical reality, and not a ‘virtual’ trial reality,” he said.

The present study showed that the presence of EGFR mutations in circulating DNA from plasma or serum can be detected in about half of patients with the testing techniques used in this study. Commenting on the study, Rafael Rosell, MD, Catalan Institute of Oncology, Barcelona, Spain, noted that since the trial was conducted, refinements in blood tests for circulating DNA have improved the sensitivity of these tests, so in the future it should be possible to do a better job at finding EGFR and other genetic mutations.

“Cell-free DNA detected in the bloodstream of cancer patients represents an excellent tool to examine genetic alterations that are usually found through tumor tissue testing. This represents one of the most astonishing phenomena in biology,” Rosell stated.

“This work paves the way for future studies and expands the routine use of examining mutations such as EGFR mutations as part of patient care,” Rosell added.

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