Refractory response to entrectinib for ROS-1 rearranged NSCLC with concurrent de novo TP53 mutation showing good response to CNS lesion, but poor duration of response: A case report.

Entrectinib, a ROS-1 inhibitor, has been shown to be effective for patients with ROS-1 fused NSCLC, and has been established as the standard of care for this population. Entrectinib has been shown to achieve a better response to brain metastasis due to the characteristic of the drug having a weak interaction with P-glycoprotein and, even in prospective studies, the intracranial response is higher. Patients have been known to acquire resistance to molecularly targeted drugs such as EGF-TKIs or ALK-TKIs during targeted therapy. Similarly, the mechanisms of resistance to entrectinib have been reported, but information about the effects of TP53 mutation with entrectinib are still limited. Here, we experienced a case of a patient with ROS-1 fusion and concurrent TP53 mutation who was treated with entrectinib, resulting in a response to brain metastasis but rapid resistance to entrectinib. Our case demonstrates both the intracranial activity of entrectinib and the potential for resistance to entrectinib due to TP53 mutation.