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

Alice Goodman

May 2015, Vol 6, No 4 - Lung Cancer

Geneva, Switzerland—Circulating DNA (ctDNA) in the blood of patients with cancer appears to detect lung cancer mutations, providing similar information to tumor tissue sampling, according to a study presented at the 2015 European Lung Cancer Conference. This makes blood testing for ctDNA an attractive option when tumor tissue sampling is not accessible.

These results have important implications for the selection of targeted therapies aimed at specific tumor mutations, said Martin Reck, MD, PhD, Department of Thoracic Oncology, LungenClinic, Grosshansdorf, Germany, who presented the study results at the European Society for Medical­Oncology.

Studies suggest that plasma ctDNA from the tumor can identify tumor mutations. 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 [computed tomography]-guided biopsy? And, are the results of this blood test in agreement with the results of the ‘gold-standard’ tissue test?” Dr Reck stated.

The investigators assessed 1162 matched tumor tissue and blood samples for the presence of an EGFR mutation in patients with lung cancer. There was an 89% agreement found between the 2 types of tests. Plasma testing identified approximately 50% of the patients with EGFR mutations compared with tumor tissue sampling, for a sensitivity of 46%.

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

The study showed that the presence of EGFR mutations in ctDNA from plasma or serum can be detected with the testing techniques used in this study in approximately 50% of patients.

Commenting on this study, Rafael Rosell, MD, PhD, Catalan Institute of Oncology, Barcelona, Spain, noted that since the trial was conducted, refinements in blood tests for ctDNA have improved the sensitivity of these tests. Therefore, in the future, using ctDNA 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,” Dr Rosell stated.

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