A rare KIF5B-ALK fusion variant in a lung adenocarcinoma patient who responded to crizotinib and acquired the ALK L1196M mutation after resistance: a case report.

An increasing number of anaplastic lymphoma kinase (ALK) gene fusion variants have been reported with the popularity of next-generation sequencing (NGS), such as striatin gene (STRN)-ALK, EMAP like 4 (EML4)-ALK and S1 RNA binding domain 1 (SRBD1)-ALK. The clinical outcomes of non-small cell lung cancer (NSCLC) patients improved dramatically with the treatment of tyrosine kinase inhibitors (TKIs), but responses to ALK-TKIs differ even for the same fusion variants with different breakpoints. The clinical effectiveness of ALK-TKIs on a new fusion variant needs to be evaluated. Here, we report a case of a lung adenocarcinoma patient, a 70-year-old nonsmoking Chinese man, with rare ALK rearrangement form of, namely, a kinesin family member 5B (KIF5B)-ALK (K20:A20) fusion which was identified in tissue by capture-based NGS. The patient achieved a partial response (PR) after treatment with crizotinib. Additionally, an ALK L1196M mutation was detected when the disease progressed after 11 months and was indicated to be sensitive to ceritinib. As far as we know, this is the first report showing that KIF5B-ALK (K20:A20) is a fusion variant that is sensitive to crizotinib. We provided a treatment strategy for managing NSCLC patients with KIF5B-ALK (K20:A20) fusion or ALK L1196M mutation after crizotinib resistance. Additionally, dynamic genomic analysis of ALK-TKIs treatments is important.