Lung Cancer: Timing May Affect EGFR mutation-related ctDNA Test Results

Timing might affect the results of an EGFR mutation–frequency circulating tumor DNA (ctDNA) test among patients with advanced NSCLC.

Timing might affect the results of an EGFR mutation–frequency circulating tumor DNA (ctDNA) test among patients with advanced non–small cell lung cancer (NSCLC), according to a study published in Thoracic Cancer.¹

EGFR mutations predict response to tyrosine kinase inhibitors (TKIs) such as gefitinib, erlotinib, and afatinib. Unlike a direct tumor biopsy, “liquid biopsies” that analyze ctDNA are a non-invasive method of detecting EGFR mutations in a patient with advanced NSCLC.

False negatives are, however, common in ctDNA tests. For this study, researchers evaluated whether sampling time within 1 day affects test results.

Twenty-two patients with stage IV NSCLC were enrolled. All patients were previously determined to harbor EGFR mutations in TKI-naive tumors and plasma.

The median mutation frequency was 7.13%. The frequency of detected mutations differed — though not significantly — between several time-points in 1 day.

One patient's mutation status changed from L858R to wild type within the 1-day period.

Gefitinib was the first-line therapy for all included patients. Patients with a mutation frequency greater than 6.76% had a better response to gefitinib than those below this threshold.

The authors noted some study limitations, which included a lack of nighttime testing and a small sample size. Nonetheless they concluded that ctDNA release may be “a temporal heterogenous process and different sampling time-points do not seem to influence [EGFR mutation] status in ctDNA.”

Reference

1. Wang J, Bai H, Hong C, Wang J, Mei TH. Analyzing epidermal growth factor receptor mutation status changes in advanced non-small-cell lung cancer at different sampling time-points of blood within one day. Thorac Cancer. 2017 Apr 24. doi: 10.1111/1759-7714.12443 [Epub ahead of print]