Lung Cancer Diagnosis in Absence of Adequate Tissue Molecular Analysis in Metastatic Disease by NGS Analysis of Plasma cfDNA

Although molecular analysis of tumor material is standard of care in patients with metastatic non-squamous non-small cell lung cancer, this is not always feasible. In daily practice it can be difficult to obtain tumor tissue or there may be insufficient tissue available for molecular investigation. This leaves possible targeted-treatment options unidentified in a subset of patients. In 2019, Erasmus MC Cancer Institute launched the project Lung Cancer Diagnosis – cfDNA (LCD-cfDNA). Hospitals in the Comprehensive Cancer Network Southwest (The Netherlands) were given the opportunity to submit plasma samples from patients in whom adequate molecular analysis in tumor tissue was not possible. Blood was collected in Cellsave preservative 10mL vacutainer tubes (CellSearch, Menarini Silicon Biosystems, Castel Maggiore, Italy) and plasma cfDNA isolation was performed by QIAmp Circulating Nucleic Acid Kit (QIAGEN). NGS analysis was conducted by semiconductor sequencing with the Ion S5 System (Thermo Fisher Scientific) and cfDNA library preparation was performed using the Oncomine Lung cfDNA Assay v1 (Thermo Fisher Scientific). Results were discussed in the Thoracic Oncology Molecular Tumor Board and reported to the referring physician. Between January 1st 2019 and January 1st 2021, plasma samples from 55 patients were submitted and analyzed. In 2 samples (3.6%), an activating EGFR aberration was detected (an exon 19 deletion in one patient; patient started on EGFR-TKI with response, and an exon 20 insertion in another patient; no treatment yet). In 4 cases (7.3%) a KRAS p.G12C and in 1 case (1.8%) an activating BRAF mutation (p.G466V) was identified in plasma (possible target for treatment in the near future). In 21 samples (38.2%) other aberrations were detected, which did not affect the choice of systemic therapy (other KRAS, TP53 and PIK3CA mutations). No mutations were found in 27 cases (49.1%).TableDetected aberrations (per sample)1EGFR p.E746_A750del2EGFR p.P770_V771insG; TP53 p.R209Qfs*73BRAF p.G466V; TP53 p.E339*4KRAS p.G12C5KRAS p.G12C; TP53 p.R267W6KRAS p.G12C; KRAS p.Q61H; TP53 p.R202C7KRAS p.G12C8KRAS p.G12D9KRAS p.G12D; PIK3CA p.E545K10KRAS p.G12V; TP53 p.C275F11KRAS p.G12V12TP53 p.G244V13TP53 p.R283C14TP53 p.Y205*; PIK3CA p.E545K15TP53 p.G266V16TP53 p.Y234C; TP53 c.672+1G>T; p.?17TP53 p.R249S18TP53 p.R158H19TP53 p.S215R20TP53 p.P278L21TP53 p.R283H22TP53 p.P278S; TP53 p.G279E; TP53 c.375+3_375+4insG; p.?23TP53 p.R267Q24TP53 p.C238F; TP53 p.C275S25TP53 p.Y163C26TP53 p.R248W27TP53 p.S241F28TP53 p.V272G Open table in a new tab For patients in whom molecular analysis on tissue cannot be performed, NGS analysis of cfDNA in plasma provides an opportunity to detect driver mutations for subsequent targeted therapy.