Rapid Response to Lenvatinib and Disease Flare Following Discontinuation in a Patient with Thymic Carcinoma Harboring KIT exon 11 Mutation: A Case Report

Lenvatinib, a multi-target tyrosine kinase inhibitor (TKI) for c-Kit and other kinases, has shown promising efficacy in treating advanced or metastatic thymic carcinoma (TC). Here, we present the case of a patient with metastatic TC harboring a KIT exon 11 deletion and amplification. The patient showed 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 KIT 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.