Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed non-small cell lung cancer

- Squamous cell carcinoma

- Adenocarcinoma (including large cell carcinoma)

- Non-small cell cancer not otherwise specified

- Brain metastases

- Biopsy not required

- Ineligible for surgical resection or radiosurgery

- Systemic disease that is not in immediate need of chemotherapy

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- Karnofsky 70-100%

Life expectancy:

- More than 12 weeks

Hematopoietic:

- Absolute neutrophil count at least 1,500/mm^3

- Platelet count at least 100,000/mm^3

- Hemoglobin at least 9 g/dL

Hepatic:

- Bilirubin no greater than 2 times upper limit of normal (ULN)

- SGOT and SGPT no greater than 2 times ULN (5 times ULN if liver metastases present)

- Alkaline phosphatase no greater than 2 times ULN (5 times ULN if liver metastases
present)

Renal:

- BUN no greater than 1.5 times ULN

- Creatinine no greater than 1.5 times ULN

Other:

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No known HIV positivity or AIDS-related illness

- No active nonmalignant systemic disease

- No frequent vomiting or other medical condition that would preclude oral medication
intake (e.g., partial bowel obstruction)

- No other prior or concurrent malignancies within the past 5 years except surgically
cured carcinoma in situ of the cervix or basal cell or squamous cell skin cancer

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- No concurrent immunotherapy or biologic therapy except growth factors

Chemotherapy:

- See Disease Characteristics

- At least 4 weeks since prior chemotherapy and recovered

- No more than 1 prior chemotherapy regimen for systemic metastatic disease

- No prior chemotherapy for brain metastases

- No prior temozolomide

- Concurrent chemotherapy (docetaxel, paclitaxel, or cisplatin) to alleviate
progressing systemic disease is allowed

Endocrine therapy:

- Concurrent dexamethasone required

Radiotherapy:

- See Disease Characteristics

- At least 4 weeks since prior radiotherapy to 15% or more of total bone marrow (2
weeks for less than 15% of bone marrow) and recovered

- No prior radiotherapy to 50% or more of total bone marrow

- No prior radiotherapy to the brain

- Prior radiotherapy for local control or palliative therapy for a painful bony lesion
allowed

- Concurrent radiotherapy to painful bony lesions allowed if no more than 15% of bone
marrow is irradiated

Surgery:

- See Disease Characteristics

- Prior surgery for brain metastases allowed

Other:

- No other concurrent investigational drugs

- Recovered from toxic effects of all prior therapies