DISEASE CHARACTERISTICS: Histologically or cytologically proven stage IV breast cancer Measurable disease after firstline or greater chemotherapy Evidence of CEA expression by: Serum CEA at least 10 ng/mL OR Positive immunostaining of primary or metastatic tumors with a CEA-specific antibody Positive imaging of at least 1 confirmed tumor by pre-therapy indium In 111 monoclonal antibody MN-14 No brain metastases Bone marrow biopsy prior to stem cell mobilization required to assess cellularity and tumor involvement Cellularity greater than 60% of normal Tumor involvement less than 25% Chromosome analysis of bone marrow aspirate (optional) No brain metastases Hormone receptor status: Not specified