The utility of sputum cell-free DNA (cfDNA) as a surrogate material for detecting EGFR mutations in lung adenocarcinoma (LAC) patients has been shown. However, it has not been documented if it is appropriate for detecting mutations in numerous driver genes.

Sputum and matched tumor samples from 83 individuals with LAC were obtained as part of the study. Sputum supernatant-derived cfDNA and matched tumor DNA were examined using next-generation sequencing (NGS)-based 10-gene panel. In addition, the sediments from the sputum were examined cytologically.

In sputum cfDNA and matching tissue samples, the overall positive rates of hotspot mutations in the 10 driver genes were 65.1% and 77.1%, respectively. Overall, the specificity was 100% and the detection sensitivity for variations in sputum cfDNA was 81.3% (95% CI, 69.2%, 89.5%). The sensitivity of testing sputum cfDNA from patients with stage IIIB-IV malignant sputum was 94.1% (95% CI, 78.9%, 99.0%); the sensitivity of testing sputum cfDNA from patients with stage IIIB-IV malignant sputum was 87.0% (95% CI, 74.5%, 94.1%); and the sensitivity of testing sputum cfDNA from patients with malignant sputum was 92.3% (95% CI, 78.0%, 98.0%).

The work showed that the discovery of many driver genes by NGS was successfully accomplished using sputum cfDNA. In particular, for patients with advanced LAC and malignant sputum, sputum cfDNA might be a good surrogate clinical material for an all-in-one evaluation of mutations to guide target therapy.

Reference: acsjournals.onlinelibrary.wiley.com/doi/10.1002/cncy.22644