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.

Inclusion Criteria:

1. Histologically or cytologically proven non small cell lung cancer
2. New developed or progression of brain lesions among patients with good control of extracranial lesions to erlotinib
3. patients who are receiving erlotinib as salvage therapy
4. At least one unidimensionally measurable lesion with a diameter > 10mm using brain MRI
5. at least on unidimensionally measurable or evaluable lesion
6. male or female patients aged >18 years
7. ECOG performance status 0-2
8. Adequate hematologic function
9. adequate renal function
10. adequate hepatic function

Exclusion criteria

1. leptomeningeal metastases
2. acute severe infection requiring antibiotic therapy
3. significant cardiovascular disease
4. uncontrolled DM
5. severe ophthalmologic disease