Rapid Response to Lenvatinib and Disease Flare After Discontinuation in a Patient With Thymic Carcinoma Harboring KIT Exon 11 Mutation: A Case Report.

Lenvatinib, a multitarget tyrosine kinase inhibitor for c-Kit and other kinases, has exhibited promising efficacy in treating advanced or metastatic thymic carcinoma (TC). Here, we present the case of a patient with metastatic TC harboring a exon 11 deletion and amplification. The patient exhibited a remarkable response to lenvatinib but experienced rapid disease progression after discontinuation of lenvatinib, referred to as a "disease flare." This case report indicates that mutations and amplification can predict lenvatinib response in patients with TC. However, in such cases, there might be a risk of disease flares after lenvatinib discontinuation.