Lometrexol Plus Folic Acid in Treating Patients With Stage IIIB or Stage IV Non-Small Cell Lung Cancer

DISEASE CHARACTERISTICS:

Histologically confirmed non-small cell lung cancer (NSCLC)

Stage IIIB or IV

Squamous cell carcinoma
Adenocarcinoma
Large cell carcinoma
Adenosquamous carcinoma
Progressive disease after receiving 1 cisplatin- or carboplatin-containing regimen for stage IIIB or IV disease

Measurable disease

At least 1 lesion at least 1 cm x 1 cm by CT scan either not in a previously irradiated field or showing clear evidence of disease progression after radiation
No symptomatic or rapidly increasing, moderate or large amounts of pleural effusion or ascites
No prior or concurrent CNS metastases (brain or meningeal)

PATIENT CHARACTERISTICS:

Age:

18 and over

Performance status:

Karnofsky 70-100%

Life expectancy:

At least 3 months

Hematopoietic:

Absolute neutrophil count at least 1,500/mm^3*
Platelet count at least 100,000/mm^3*
Hemoglobin at least 9.0 g/dL*
*Without transfusions or growth factors in the previous 7 days

Hepatic:

Bilirubin no greater than 1.5 times upper limit of normal (ULN) (regardless of liver involvement secondary to tumor)
AST and ALT no greater than 2.5 times ULN (5 times ULN if liver has tumor involvement)

Renal:

Calculated creatinine clearance at least 60 mL/min using Cockroft and Gault formula

Gastrointestinal:

No inflammatory bowel disease
No radiation enteritis
No malabsorption syndrome
No inability to absorb folic acid

Other:

Not pregnant or nursing
Negative pregnancy test
Fertile patients must use effective contraception during study
No known untreated vitamin B12 deficiency
HIV negative
No drug abusers
No prior malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix
No severe concurrent disease or major comorbidity that would preclude study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy:

At least 3 weeks since prior biologic therapy for NSCLC and recovered from acute side effects
Prior treatment with an experimental vaccine allowed
No concurrent routine or prophylactic filgrastim (G-CSF), sargramostim (GM- CSF), or epoetin alfa

Chemotherapy:

See Disease Characteristics
At least 3 weeks since prior chemotherapy for NSCLC (6 weeks for mitomycin or nitrosourea) and recovered from acute side effects
Prior adjuvant or neoadjuvant chemotherapy allowed

Endocrine therapy:

Not specified

Radiotherapy:

See Disease Characteristics
Recovered from acute side effects of prior radiotherapy
No prior radiotherapy to 25% or more of bone marrow
No prior whole pelvic irradiation

Surgery:

At least 3 weeks since prior major surgery and recovered

Other:

At least 3 weeks since prior investigational agent
No concurrent proguanil, trimethoprim, co-trimoxazole, or pyrimethamine