Liquid biopsy analysis of ALK alterations from advanced NSCLC patients: The value of exosomal RNA cargo (ExoALK).

Abstract

e20569 Background: About 5% of NSCLCs present alterations in the ALK gene. Among them the most common is EML4-ALK translocation. The gold standard detection method to treat the patient with ALKi is the tissue, thus, it is mandatory to develop new techniques that allow to detect ALK alterations in liquid biopsy. The purpose of this study is, analyze the feasibility to detect ALK alterations in exosomes (Exo-ALK) derived from NSCLC patients. Methods: We recruit 18 NSCLC patients including EML4-ALK and wild-type patients stage- and time-independent. ALK-positive status is identified by IHQ. The isolation of RNA with the exoRNeasy Kit Serum/Plasma (Qiagen) in UZA and the retrotranscription with ProtoScript II First Strand cDNA Synthesis kit. The ALK alteration present in the exosomes is determined by NGS and bio-informatic analysis in OncoDNA. Samples were provided by the Biobank of the University of Navarra, the UZA Biobank and the University of Naples Federico II. Samples and data were processed following the processes approved by the local Ethical and Scientific Committees. Results: Among analyzed patients, 15 patients were EML4-ALK tissue positive, and 3 were EML4-ALK tissue negative. With our analysis, 9 patients were positive, 7 negative and 2 sample were degraded at the time of analysis. Comparing the results, the 9 positive patients in the exosomes were also positive in the tissue. Moreover, the 2 negative patients were also negative for the translocation in the tissue. However, we were unable to detect 4 positive EML4-ALK patients in the exosomes. Nonetheless, these data show a sensitivity of 69% and a specificity of 100%. No correlation was found comparing treatment-naïve and pretreated patients. Conclusions: Exosomes are raising as a very promising tool to determine the tumor profile due to their stability and their cargo. With further study and a larger number of patients, we demonstrate that exosomes isolation and analysis will be feasible tool, and thus we will reduce the tumor biopsy risks and costs in the clinical practice. Our preliminary results show a good specificity for a proof of concept analysis. These results will be cross-validated and amplified with more patients in the following months.