Background Crizotinib is a standard of care in anaplastic lymphoma kinase(ALK)-positive advanced non-small-cell lung cancers (NSCLC).Undoubtedly, the resistance to crizotinib is a current bottleneck. Hence, it is necessary to explore the resistance mechanisms to ALK inhibitors.

Method From October 2010 to May 2017,225 ALK-positive NSCLC patients treated with crizotinib were reviewed at the Guangdong General Hospital in China. The status of ALK rearrangement was assessed by Lysis ALK Break Apart fluorescence in situ hybridization, reverse transcription polymerase chain reaction ,or Ventana ALK immunohistochemistry. Next generation sequencing(NGS) was used to test the tissue or plasma from patients with resistance to crizotinib. Primary resistance to crizotinib occurred when Progression-free survival was less than 3 months for the patients treated with crizotinib.

Result Among enrolled patients, 72.4%(163/225) gained secondary resistance, and 8.9%(20/225) had primary resistance. Molecular mechanisms of clinically primary resistance were shown in Fig a. The variants of ALK fusion were different between primary and secondary resistance patients. There were more variants of ALK fusion appeared in the group with primary resistance except E6-A20 and E13-A20.Among secondary resistant patients，non-EML4 partners fusion, such as DMD-ALK fusion,YWHAQ&TAF1B-ALK fusion, GALNT14-ALK fusion and SLC19A3-CCL20-ALK fusion were found, which responded to crizotinib treatment. Acquired ALK L1196M/G1269A mutations were found in both primary and secondary resistant patients, and while ALK I1171T mutation was only found in secondary resistant patients. Wnt signaling pathway was activated significantly after the treatment of crizotinib according to Kyoto Encyclopedia of Genes and Genomes(KEGG) and GeneOntology(GO) analyzes. Moreover, AMER1 aberrance was inclined to appear in the primary resistance patients, which was significant different between the two groups in KEGG and GO analyzes.

Conclusion ALK mutations could exist in both primary and secondary resistance to crizotinib in ALK-rearranged NSCLC. Response to crizotinib was also observed in ALK-rearranged NSCLC patients with non-EML4 partners. NGS may facilitate precision treatment for both primary and secondary resistant patients though they have a few differences in molecular mechanisms of resistance.

Keywords Resistance to ALK inhibitors