About 80% to 85% of lung cancers are non-small cell lung cancer (NSCLC). EGFR tyrosine kinase inhibitors as well as several other targeting molecules have been demonstrated to be effective in treating patients with activating mutations. We investigated the use of circulating tumor DNA (ctDNA) and high sensitive detection techniques for mutational profiling to improve the diagnosis and monitoring of NSCLC patients.
ctDNA was extracted from plasma using the QIAamp Circulating Nucleic Acid kit (Qiagen). A custom panel was designed to cover EGFR, KRAS, NRAS, BRAF, PIK3CA, DDR2, AKT1, PTEN, MEK1 and ERBB2 hotspot mutations. Libraries, constructed according to the AmpliSeq protocol, were sequenced on the semiconductor Ion Torrent S5XL platform. The presence of the EGFR T790M mutation was also assessed by a digital PCR assay.
A total of 120 patients from 30 Belgian institutions were enrolled in this prospective study. The majority of patients presented with stage IV adenocarcinoma and progression. Forty-six (46) patients had a mutation detected on a former biopsy: EGFR exon 19 (26), EGFR exon 21 (8), KRAS (10), PIK3CA (1) and ERBB2 (1). Among those patients, 28 (61%) harbored the same mutation when their ctDNA was sequenced with our NGS panel: EGFR exon 19 (15), EGFR exon 21 (6), KRAS (5), PIK3CA (1) and ERBB2 (1). For 7 patients, for which no mutation had not been previously detected, 4 EGFR, 2 KRAS and 1 NRAS mutations were found after ctDNA analysis. As far as the ddPCR detection of EGFR T790M was concerned, the mutation was detected on 7 (21%) of the 34 patients presenting EGFR mutations in their prior biopsy (5 in exon 19 and 2 in exon 21). Patients with acquired T790M mutation were previously treated by Afatinib (3), Erlotinib (2) or Gefitinib (1).
Our results indicate that ctDNA can be an alternative and noninvasive source of tumor DNA, a surrogate to classical biopsies, particularly when access to tumor tissue is limited. NGS and ddPCR assays are sensitive enough to promote a clinical translation of ctDNA analysis into disease management and therapeutic decision. Supported by a grant from Boehringer Ingelheim.
Clinical trial identification
Legal entity responsible for the study
Institut de Pathologie et de Génétique
Boehringer Ingelheim Institut de Pathologie et de Génétique
All authors have declared no conflicts of interest.