DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed stage III or IV non-small cell lung cancer (NSCLC)
• Received or plan to receive 1 and only 1 chemotherapy regimen with or without thoracic radiotherapy as first-line therapy for NSCLC
• Disease must be stable or responding after prior or planned chemotherapy for 3-6 months
• No untreated brain metastases

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• ECOG 0-2

Life expectancy:

• At least 3 months (patients who have received first-line therapy) OR
• At least 6 months (patients who plan to receive first-line therapy)

Hematopoietic:

• Absolute neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3
• Hemoglobin at least 10.0 g/dL

Hepatic:

• Bilirubin no greater than 1.5 times upper limit of normal (ULN)
• AST no greater than 3 times ULN
• Alkaline phosphatase no greater than 3 times ULN

Renal:

• Creatinine no greater than 1.5 times ULN

Other:

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 2 months after study

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• No other concurrent immunotherapy

Chemotherapy:

• See Disease Characteristics
• Prior radiosensitizers allowed
• No more than 6 weeks since prior chemotherapy
• No concurrent chemotherapy

Endocrine therapy:

• Not specified

Radiotherapy:

• See Disease Characteristics
• No more than 6 weeks since prior thoracic radiotherapy
• No concurrent radiotherapy

Surgery:

• Not specified

Other:

• No concurrent participation in another phase III lung cancer treatment trial