EGFR exon 20 insertion mutation in advanced thymic squamous cell carcinoma: Response to apatinib and clinical outcomes.

Thymic carcinoma (TC) is a rare malignant tumor of the mediastinum with occult onset, rapid development, and poor prognosis. Surgery is the main treatment for early TC, but the majority of patients are diagnosed at Masaoka-Koga stage III or IV with local invasion or distant metastasis. Platinum and anthracyclines are currently considered key components of first-line chemotherapy for advanced TC; however, there are no standard treatment plans for patients who are refractory to first-line and further chemotherapy. The clinical effect is also unsatisfactory. Apatinib has been successfully applied as third-line treatment for advanced gastric cancer and has shown high efficacy in the treatment of various cancers, such as lung, liver, and colorectal cancers. Herein we report a case of advanced thymic squamous cell carcinoma harboring EGFR exon 20 insertion in which apatinib was administered after multi-line chemotherapy and radiotherapy and a partial response was achieved after five months of treatment. To date, a five month overall response and 10 months of progression-free survival have been achieved. Adverse reactions can be controlled and the patient's quality of life has improved. Apatinib provides a new option for clinicians to treat patients with advanced TC.