Stereotactic radiosurgery (SRS) using the Gamma Knife (GK) is now being 
increasingly utilized for the treatment of brain metastases. However, there are 
a few reported cases of SRS-induced brain neoplasms. We herein report the case 
of a Japanese woman with metastatic non-small cell lung cancer (NSCLC) harboring 
epidermal growth factor (EGFR)-mutations who was treated four times with a GK 
for brain metastases. She developed glioblastoma 5.7 years after the initial GK 
surgery. Radiation-induced secondary neoplasms generally appear after a latency 
period of several years. Advances in cancer therapy have improved the survival 
of patients with NSCLC, providing enough time for secondary neoplasms to appear 
after SRS.