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Abstract 467: DetectingALKrearrangement by RT-PCR: A superior approach to next generation sequencing

Background: Precisely detecting anaplastic lymphoma kinase (ALK) rearrangement ensures ideal efficacy of ALK targeted tyrosine kinase inhibitors (ALK-TKIs). Next generation sequencing (NGS) has been widely used in clinics, while, numbers of studies indicated NGS would yield false negative outcome, especially for fusion analysis. Instead, more fusions can be detected by RT-PCR at transcription level. This study aims to compare the capacity of RT-PCR and NGS approach to detect ALK rearrangement in Chinese non-small-cell lung cancer (NSCLC) patients. Methods: Formalin-fixed paraffin-embedded (FFPE) tissues from 153 patients pathologically diagnosed as NSCLC with eligible ALK status given by previous NGS testing (29 patients were ALK positive and 124 patients were ALK negative) were collected from November 2017 to October 2019. RT-PCR were applied to detect ALK rearrangements in both groups. For samples with discordant result of ALK status, fluorescence in situ hybridization (FISH) or Sanger9s sequencing were used for validation. Results: One hundred and twenty-four samples (26 of 30 ALK positive samples; 98 of 124 ALK negative samples) were successfully subjected to RT-PCR. Five of 98 ALK negative samples given by NGS test were re-defined as ALK positive by RT-PCR. Meanwhile, in 26 ALK positive samples, RT- PCR yielded acceptable result with 96.15% of concordance rate. Only one NGS-defined ALK positive sample was uncovered by RT-PCR due to a rare ALK rearrangement. Four of 6 RT-PCR defined ALK positive cases (3 RT-PCR positive and 1 NGS positive) were validated by either FISH or sanger9s sequencing, which resulted positive result. Conclusions: RT-PCR displays reliable and superior capacity to detect ALK fusion in NSCLC patients. Citation Format: Yukun Kuang, Peihang Xu, Jiyu Wang, Yifan Zheng, Xue Sun, Zimu Li, RunJing Gan, Huixia Li, Yubiao Guo, Guanshan Zhu, Changbin Zhu, Zunfu Ke, Kejing Tang. Detecting ALK rearrangement by RT-PCR: A superior approach to next generation sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 467.