Detecting therapy-guiding RNA aberrations in platelets of non-small cell lung cancer patients

Abstract

Background Nowadays, the detection of therapy-guiding aberrations such as EGFR mutations and ALK fusion genes in tumor tissue is common practice for lung cancer patients. The aim of this study is to explore the feasibility of detecting common therapy-guiding aberrations in RNA isolated from platelets. Methods We applied a single primed enrichment-based targeted next generation sequencing (NGS) approach on 10 platelet RNA samples isolated from patients with active disease. In parallel, we applied RNA-based ddPCR focusing on EGFR p.(T790M), p.(L858R) and E19del, on KRAS codon 12 and 13 and on ALK-EML4/KIF5B fusions on 22 platelet RNA samples from patients with tumors known to harbor one of these drivers. For 11 cases ddPCR analysis of circulating cell free (cf)DNA from the same blood sample was performed in parallel. Results Despite having good quality NGS data, none of the variants detected in the tumor biopsy were observed in platelet-derived RNA samples. Using the more sensitive ddPCR, we detected known aberrations in three of 22 platelet-derived RNA samples. EGFR mutant droplets were not observed in any of the seven platelet samples, while these mutations were detected in three of six cfDNA samples of which five were extracted from the same blood sample. KRAS mutant droplets were detected in three out of nine platelet RNA samples with fractional abundances of 0.07%, 0.11% and 0.55%. Analysis of five cfDNA samples from the same blood samples revealed KRAS-mutant droplets in four of them. Two of the four corresponding platelet RNA samples were also positive for mutant KRAS. No ALK fusion droplets were detected in seven platelet derived RNA samples. Conclusions The level of tumor-derived RNA transcripts in platelets of non-small cell lung cancer patients was too low to be measured reliably for clinically relevant alterations in EGFR, KRAS and ALK fusion gene transcripts. Keywords: non-small cell lung cancer, platelet RNA, ALK, EGFR, KRAS