Case Report: A rare case of ALK-KIF5B gene fusion benefited from treatment with lorlatinib.

The anaplastic lymphoma kinase () gene encodes a transmembrane receptor tyrosine kinase. Most mutations in gene result from translocations with other genes, forming fusion oncogenes. To date, 21 different genes have been identified as fusion partners, each activating distinct signaling pathways that influence cancer cell proliferation, invasiveness, and tumorigenicity. tyrosine kinase inhibitors (ALK-TKIs) have demonstrated significant efficacy in -positive non-small cell lung cancer (NSCLC) and are widely utilized as first-line therapy. Lorlatinib, a third-generation ALK inhibitor, is effective in both treatment-naïve and previously treated patients with advanced NSCLC, exhibiting strong systemic and intracranial antitumor activity. This report presented a case of lung adenocarcinoma with 51 genetic variants, including a rare fusion variant: exon 15 of fused to exon 20 of , KIF5B-ALK (K15:A20). Following lorlatinib treatment, partial remission was achieved, and disease stability was maintained for an extended period, suggesting a favorable response to therapy. This case highlighted the potential sensitivity of the (K15:A20) fusion to lorlatinib and the need for further investigation into lorlatinib's efficacy across different fusion variants. Additionally, other fusion types and treatment options for fusions with varying breakpoints were discussed.