Oncotarget
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Cancer treatment is evolving towards therapies targeted at specific molecular abnormalities that drive tumor growth. Consequently, to determine which patients are eligible, accurate assessment of molecular aberrations within tumors is required. Obtaining sufficient tumor tissue for molecular testing can present challenges; therefore, circulating free tumor-derived DNA (ctDNA) found in blood plasma has been proposed as an alternative source of tumor DNA. ⋯ We conclude that there are several advantages associated with ctDNA, including the potential for repeated sampling - particularly following progression after first-line tyrosine kinase inhibitor (TKI) therapy, as TKIs targeting resistance mutations (eg T790M) are now approved for use in the USA/EU/Japan (at time of writing). However, evidence suggests that ctDNA does not allow detection of EGFR mutations in all patients with known mutation-positive NSCLC. Therefore, although tumor tissue should be the first sample choice for EGFR testing at diagnosis, ctDNA is a promising alternative diagnostic approach.