Use of a plasma test for verifying epidermal growth factor receptor gene (EGFR) mutations in fluid samples from non-small cell lung cancer patients()

Because epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are effective in the treatment of non-small cell lung cancer (NSCLC) patients with EGFR mutations, it is critical to obtain accurate EGFR mutation test results. For NSCLC patients, EGFR mutation testing is performed using the commercial Cobas EGFR Mutation test v2.0, which can be used to analyze both formalin-fixed, paraffin-embedded (FFPE) tissue (FFPE test, or FT) and plasma samples (plasma test, or PT). Since primary tumor tissues are often unavailable from relapsed patients, fluid samples are often used for EGFR mutation testing, but they are often tested using the FT. Here, we report three cases in which EGFR mutations were detected using the FT with FFPE primary tumor tissue samples, but were not detected using fluid samples (two pleural effusion and one cerebrospinal fluid sample). Because the FT may not be capable of detecting EGFR mutations in fluid samples, we used the PT, which is more sensitive, to verify the presence of EGFR mutations using the same fluid samples. As expected, the PT detected the same EGFR mutations in fluid samples as the FT did in FFPE primary tumor tissue samples.