Monitoring of epidermal growth factor receptor tyrosine kinase inhibitor-sensitizing and resistance mutations in the plasma DNA of patients with advanced non-small cell lung cancer during treatment with erlotinib

Abstract

Background: The feasibility of monitoring epidermal growth factor receptor (EGFR) mutations in plasma DNA from patients with advanced non-small cell lung cancer (NSCLC) during treatment with erlotinib and its relation to disease progression was investigated.

Methods: The amount of EGFR-mutant DNA was tested in plasma DNA from patients with advanced NSCLC with allele-specific polymerase chain reaction assays. Blood samples from 23 patients with adenocarcinoma of NSCLC that carried tyrosine kinase inhibitor-sensitizing EGFR mutations were taken immediately before treatment with erlotinib. Additional blood samples were taken at timed intervals until erlotinib treatment was withdrawn.

Results: The amount of plasma DNA with sensitizing EGFR mutations was found to be reduced after the first cycle of erlotinib treatment in 22 of 23 patients (96%). No patients presented with the resistant T790M mutation in the pretreatment sample, but at the time of disease progression the mutation was detected in plasma from 9 patients (39%). The quantitative data from the current study demonstrated that when a T790M mutation emerged in the blood it was accompanied by an increase in the original sensitizing EGFR mutation. When T790M was detected, it was found to be present in all subsequent blood samples from that patient. Most interestingly, the results of the current study demonstrated that monitoring the EGFR mutations in the blood allows for the detection of the T790M mutation up to 344 days before disease progression is clinically evident (range, 15-344 days).

Conclusions: The results of the current study demonstrated that serial monitoring of EGFR mutations in plasma DNA is feasible and may allow for the early detection of resistance mutations. These results warrant further studies to explore the clinical usefulness of such analysis.

Trial registration: ClinicalTrials.gov NCT00815971.

Keywords: epidermal growth factor receptor (EGFR) mutations; erlotinib; lung cancer; plasma DNA; resistance.

Figure 1

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.