Catalog of 5' Fusion Partners in ALK-positive NSCLC Circa 2020

Since the discovery of anaplastic lymphoma kinase fusion-positive (ALK+) NSCLC in 2007, the methods to detect ALK+ NSCLC have evolved and expanded from fluorescence in situ hybridization and immunohistochemistry to next-generation DNA sequencing, targeted RNA sequencing, and whole transcriptome sequencing. As such, the deep sequencing methods have resulted in the expansion of distinct fusion partners identified in ALK+ NSCLC to 90 (one variant PLEKHM2-ALK is found in small cell lung cancer but included in this catalog) by the end of January 2020; about 65 of them (since 2018) and most of the recent novel fusion partners were reported from China. Thirty-four of the distinct fusion partners are located on the short arm of chromosome 2; 28 of these 34 fusion partners are located on 2p21-25, in which ALK is located on 2p23.2-p23.1. Many of these new ALK+ NSCLC fusion variants have responded to ALK tyrosine kinase inhibitors (TKIs). Several of these novel ALK fusion variants were identified as being resistant to EGFR TKIs or as dual 3'ALK fusions. In addition, at least 28 intergenic ALK rearrangements have also been reported, with three of them reported as responding to crizotinib. This review aims to serve as a central source of reference of fusion partners in ALK+ NSCLC for clinicians and scientists. We aim to update and improve the list going forward.