DISEASE CHARACTERISTICS: Diagnosed breast cancer at high risk for disease recurrence with one of the following requirements: Disease free stage IV breast cancer following eradication of disease by surgery, radiotherapy, or chemotherapy Stage I, II, or III breast cancer remaining clinically free of identifiable disease following adjuvant chemotherapy with 2 consecutively rising CA15.3 (BR2729) or CEA levels at least 2 weeks apart Elevation of marker levels not needed for stage III disease if adjuvant therapy completed within past 2 years CEA increase at least 1.5 times upper chronic value in patients with significant smoking history and chronic CEA elevation less than 15 Recurrence in the ipsilateral axilla following lumpectomy/axillary dissection or modified radical mastectomy Recurrence in the ipsilateral breast following lumpectomy/axillary dissection Stage II disease with at least 4 positive axillary lymph nodes and adjuvant therapy completed within past 2 years Stable stage IV disease on hormonal therapy Colonoscopy required for isolated CEA elevation Hormone receptor status: Not specified