Abstract A33: Utility of multiplexed biomarker analysis in non-small-cell lung cancer patients with discrepancies between FISH and immunohistochemical results of ALK testing

Abstract

Abstract Background: The clinical implications in Non-small cell lung cancer (NSCLC) patients with discrepancy between fluorescent in situ hybridization (FISH) and immunohistochemistry (IHC) assessing ALK status are unclear. Materials and Methods: From 1131 archived tissue samples, we identified 41 NSCLC patients with discrepant results showing positive or borderline ALK FISH and negative IHC using ALK1 antibody. Of these, 21 cases with sufficient tissue remaining for selected reaction monitoring (SRM) and an additional case within normal range FISH split (4%) were sent to confirm ALK IHC using other antibodies (5A4 and D5F3). Target protein levels measured by multiplexed SRM were correlated with records of clinical outcomes after treatment with crizotinib or cytotoxic chemotherapy. Results: Of 22 cases with various ALK FISH results and negative IHC (ALK1), IHC using other antibodies (5A4 and D5F3) identified 4 positive cases, whereas the SRM assay identified 7 cases with tumor-specific ALK protein. IHC showed lower sensitivity in specimen with delayed fixation but SRM showed superior sensitivity in those samples as SRM is independent to modified epitope. Of 8 crizotinib-treated cases, 4 cases with detectable levels of either ALK or cMET proteins had complete or partial responses; cases without either of these proteins (n = 4) did not respond to crizotinib regardless of ALK FISH results. Cases with 3 or more predictive proteins specific to chemotherapeutic agents were found to be more responded to those agents and had a higher probability of progression-free survival. Conclusions: The SRM assay showed superior sensitivity in poorly fixed specimens and can inform therapeutic decision-making in NCSLC patients with ALK screening discordances. Citation Format: TAE-JUNG KIM, HIDEKI TERAI. Utility of multiplexed biomarker analysis in non-small-cell lung cancer patients with discrepancies between FISH and immunohistochemical results of ALK testing. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A33.