Newly developed or progressive brain metastasis during erlotinib treatment is considered
progressive disease requiring change of treatment regimens despite no progression in
extracranial lesions. Given that there is a dissociation in terms of response to erlotinib
between brain and extracranial sites, we intend to conduct this pilot study to determine
whether the continuation of erlotinib treatment can prolong the progression free interval of
extracranial lesions as long as cranial lesion is controlled separately by conventional
treatment modalities such as surgical resection, stereotactic radiosurgery, and whole brain
radiotherapy.