DISEASE CHARACTERISTICS: Histologically or cytologically confirmed non-small cell lung cancer Stage IIIA/B disease No malignant pleural effusions Minimal residual disease after one or a combination of the following: Incomplete surgical resection i.e., macroscopic residual disease at completion of surgery Radical radiotherapy with no evidence of disease progression at entry Documented complete or partial tumor response following at least 2 courses of cytotoxic chemotherapy No evidence of disease progression during or following prior therapy