Inclusion Criteria:

- Histologically confirmed non-small cell lung cancer

- One to 3 intraparenchymal brain metastases by contrast-enhanced MRI, meeting the
following criteria:

- Well circumscribed tumor(s)

- Maximum diameter ≤ 4.0 cm

- If multiple lesions are present and one lesion is at the maximum diameter,
the other lesions must be ≤ 3.0 cm in maximum diameter

- No metastases within 10 mm of the optic apparatus such that a portion of the
optic nerve or chiasm would be included in the high-dose stereotactic
radiosurgery boost field

- No metastases in the brainstem, midbrain, pons, or medulla

- No prior complete resection of all known brain metastases

- Subtotal resection allowed provided residual disease is ≤ 4.0 cm in maximum
diameter

- No clinical or radiographic evidence of progression (other than study lesion[s])
within the past month

- Patients with brain metastases at initial presentation do not require 1 month of
scans documenting stable disease

- Stable extracranial metastases allowed

- No known or pre-existing liver metastases

- No leptomeningeal metastases by MRI or cerebrospinal fluid evaluation

- Synchronous brain metastases at initial diagnosis allowed

- Performance status - Zubrod 0-1

- Hemoglobin ≥ 8 g/dL

- Absolute neutrophil count ≥ 1,000/mm^3

- Platelet count ≥ 100,000/mm^3

- AST < 2 times upper limit of normal (ULN)

- Alkaline phosphatase < 2 times ULN unless due to elevated bone metastases

- Total bilirubin normal

- Lactic dehydrogenase < 2 times ULN

- Creatinine < 1.5 times ULN

- No clinically active interstitial lung disease

- Chronic stable asymptomatic radiographic changes allowed

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- HIV negative

- Neurologic function status 0-2

- No other major medical illness or psychiatric impairment that would preclude study
participation

- No history of allergic reaction attributed to compounds of similar chemical or
biologic composition to erlotinib or temozolomide

- No concurrent immunotherapy

- No concurrent biologic therapy, excluding growth factors and epoetin alfa

- No prior temozolomide or erlotinib

- No other concurrent chemotherapy during study radiotherapy

- Other concurrent chemotherapy allowed after study radiotherapy, except for the
following:

- Temozolomide or erlotinib (arm I only)

- Erlotinib (arm II only)

- Temozolomide (arm III only)

- No prior cranial radiotherapy

- No concurrent intensity-modulated radiotherapy

- Concurrent radiotherapy to painful bone lesions allowed

- No concurrent radiotherapy to more than 15% of bone marrow

- No other concurrent therapy for brain metastases unless a recurrence is detected

- More than 30 days since prior investigational drugs

- No concurrent enzyme-inducing antiepileptic drugs including, but not limited to, any
of the following (for patients randomized to receive erlotinib):

- Phenytoin

- Carbamazepine

- Rifampin

- Phenobarbital

- Primidone

- Oxcarbazepine

- No other concurrent investigational drugs

- No concurrent Hypericum perforatum (St. John's wort)

- No drugs that alter gastric pH (e.g., proton pump inhibitors or H2 antagonists)
within 4 hours after erlotinib administration (arm III patients only)