DISEASE CHARACTERISTICS:

• 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

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• Zubrod 0-1

Life expectancy

• Not specified

Hematopoietic

• Hemoglobin ≥ 8 g/dL
• Absolute neutrophil count ≥ 1,000/mm^3
• Platelet count ≥ 100,000/mm^3

Hepatic

• 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

Renal

• Creatinine < 1.5 times ULN

Pulmonary

• No clinically active interstitial lung disease

  • Chronic stable asymptomatic radiographic changes allowed

Other

• 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

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No concurrent immunotherapy
• No concurrent biologic therapy, excluding growth factors and epoetin alfa

Chemotherapy

• 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)

Endocrine therapy

• Not specified

Radiotherapy

• 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

Surgery

• See Disease Characteristics

Other

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