DISEASE CHARACTERISTICS: Histologically proven stage IV breast cancer presenting as primary metastatic disease or with recurrence after an initial diagnosis of localized disease Enrollment in protocol for high dose chemotherapy with stem cell rescue using the "STAMP V" regimen (cyclophosphamide, thiotepa, and carboplatin) No enrollment in research transplant protocol whose primary endpoint is response duration or recovery time from toxic effects No brain or CNS metastases Hormone receptor status: Not specified