PMC

Amount of mutated epidermal growth factor receptor (EGFR) DNA is shown in the plasma isolated from patients with lung cancer who were treated with erlotinib. (A) Results from patients harboring the EGFR resistance mutation T790M (9 patients) are shown. Red line indicates T790M mutation; blue line, EGFR-sensitizing deletion in exon 19; green line, EGFR-sensitizing mutation L858R. (B) Patients in whom EGFR mutations were recorded only in the pretreatment sample (5 patients) are shown. Yellow line indicates 2 patients with identical values. (C) Patients with EGFR-sensitizing mutations present in >1 sample (8 patients) are shown. In panels A to C, the x-axis is the time from the initiation of treatment in days and the y-axis is the estimated copy number for the indicated mutations. Quantitative amounts of tumor DNA are shown for 22 of the 23 patients. The single patient with an L861Q mutation could not be quantitated. For clarity, the presentation of the different patients was done with different scaling of the x-axis and the y-axis. (D) The time point for the earliest identification of the T790M mutation in the blood and the time point for the identification of disease progression with scanning (Response Evaluation Criteria In Solid Tumors [RECIST] criteria) were determined. The figure demonstrates how many days earlier the T790M mutation could be detected in the blood before disease progression could be identified by scanning.