Abstract
In non-small cell lung cancer (NSCLC) the usage of plasma-derived circulating tumor DNA (ctDNA) have come into focus to obtain a comprehensive genetic profile of a given lung cancer. Despite the usage of specific sampling tubes, archived plasma samples as well as inappropriately treated blood samples still cause a loss of information due to cell lysis and contamination with cellular DNA. Our aim was to establish a reliable protocol to rescue ctDNA from such non-informative samples to monitor the mutational landscape in NSCLC. As a proof-of-concept study we used archived plasma samples derived from whole blood EDTA samples of 51 patients suffering from NSCLC. Analysis of the isolated plasma DNA determined only a small fraction of ctDNA in a range of 90–250 bp. By applying a specific purification procedure, we were able to increase the informative ctDNA content and improve in a cohort of 42 patients the detection of driver mutations from 32% to 79% of the mutations found in tissue biopsies. Thus, we present here an easy to perform, time and cost effective procedure to rescue non-informative ctDNA samples, which is sufficient to detect oncogenic mutations in NGS approaches and is therefore a valuable technical improvement for laboratories handling liquid biopsy samples.
Highlights
Lung cancer is the leading cause in cancer related deaths throughout the world, with non-small cell lung cancer (NSCLC) being the most common subtype [1,2]
To analyze the applicability of archived plasma samples for mutational testing, a total of 51 patients suffering from NSCLC of the histological subtype adenocarcinoma and squamous cell carcinoma were included in a proof-of-concept study
As blood sampling and plasma preparation was performed before liquid biopsy analysis was part of the routine laboratory setup, the regulations regarding processing, shipping and storage time of the blood samples prior to plasma preparation was less well defined
Summary
Lung cancer is the leading cause in cancer related deaths throughout the world, with non-small cell lung cancer (NSCLC) being the most common subtype [1,2]. During the last years several oncogenic mutations and genetic rearrangements have been discovered in NSCLC, with EGFR, KRAS, ALK, MET, BRAF, PIK3CA, ROS1, HER2 and RET being the most abundant alterations in NSCLC adenocarcinoma [4]. Some of these oncogenic mutations, e.g., EGFR L858R, can be targeted with specific tyrosine kinase inhibitors [5]. Tumor heterogeneity is common in NSCLC samples, and mutational profiles vary between different metastatic sites or even between different subclones in one site leading to an intra-individual
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