DISEASE CHARACTERISTICS: Histologically or cytologically confirmed non-small cell lung cancer Adenocarcinoma, squamous large cell, or mixed cell histology Patients with nonadenocarcinomatous disease must have evidence of carcinoembryonic antigen (CEA) production or expression documented by one of the following: Serum CEA at least 10 ng/mL Positive immunohistology of either the primary tumor or a metastasis with CEA-specific monoclonal antibody Must have received at least one prior regimen of standard chemotherapy and, if indicated, no greater than 6,900 cGy thoracic radiotherapy Patients with stage IIIA/B unresectable disease who received prior radiotherapy must show evidence of progressive disease (greater than 25% increase in primary tumor or appearance of new lesions) Patients with stage IIIB or IV disease who received no prior radiotherapy to the primary or index lesion must show evidence of stable or progressive disease by CT scans at least 4 weeks apart Less than 25% tumor involvement in bone marrow No known, active brain metastases