Temozolomide in Treating Patients With Relapsed or Progressive Small Cell Lung Cancer

DISEASE CHARACTERISTICS: Histologically or cytologically confirmed relapsed or progressive small cell lung cancer Classical or intermediate variant OR Relapsed or progressive extrapulmonary small cell carcinoma of unknown origin Bidimensionally measurable disease At least 1 cm by 1 cm by physical exam or radiologic exam Outside prior radiation port unless clinical evidence of disease progression Previously radiated brain metastases allowed provided stable or improved PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: More than 12 weeks Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 2 times upper limit of normal (ULN) SGOT/SGPT no greater than 3 times ULN (5 times ULN if liver metastases present) Alkaline phosphatase no greater than 5 times ULN Renal: Creatinine no greater than 2 mg/dL Other: HIV negative No AIDS-related illness No frequent vomiting or medical condition that would interfere with oral medication administration (e.g., partial bowel obstruction) No active nonmalignant systemic disease that would preclude study No other active invasive malignancy within the past year or concurrently requiring ongoing treatment Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception for at least 1 month before, during, and for at least 3 months after study PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior biologic therapy No concurrent immunotherapy No concurrent biologic therapy Concurrent epoetin alfa allowed Chemotherapy: At least 4 weeks since prior chemotherapy No more than 1 prior continuous or discontinuous chemotherapy regimen for metastatic disease No other concurrent chemotherapy Endocrine therapy: Concurrent hormonal therapy to boost appetite allowed (e.g., corticosteroids or medroxyprogesterone) Radiotherapy: See Disease Characteristics At least 4 weeks since prior radiotherapy to 15% or more of bone marrow At least 1 week since prior radiotherapy to less than 15% of bone marrow No prior radiotherapy to 50% or more of bone marrow No concurrent radiotherapy Surgery: Not specified Other: Recovered from prior therapy No other concurrent investigational drugs Concurrent pamidronate allowed