Stem cell transplantation for metastatic breast cancer: analysis of tumor contamination

The purpose of this study was to determine the efficacy, engraftment kineti cs, effect of bone marrow tumor contamination, and safety of high-dose ther apy and granulocyte-colony stimulating factor (G-CSF) mobilized peripheral blood progenitor cell (PBPC) support for patients with responding metastati c breast cancer. Forty two patients underwent G-CSF (10 mu g/kg) stimulated PBPC harvest. PBPC and bone marrow aspirates were analyzed by histologic a nd immunocytochemical methods for tumor contamination. Thirty-seven patient s received high-dose therapy consisting of cyclophosphamide 6 g/m(2), thiot epa 500 mg/m(2), and carboplatin 800 mg/m(2) (CTCb) given as an infusion ov er 4 d followed by PBPC reinfusion and G-CSF (5 mu g/kg) support. No transp lant related deaths or grade 4 toxicity was recorded. CD34+ cells/kg infuse d was predictive of neutrophil and platelet recovery. With a median follow- up of 38 months, three year survival was 44% with relapse-free survival of 19%. Histological bone marrow involvement, found in 10 patients, was a nega tive prognostic factor and was associated with a median relapse-free surviv al of 3.5 months. Tumor contamination of PBPC by immunohistochemical staini ng was present in 22.5% of patients and found not to be correlated with dec reased survival. G-CSF stimulated PBPC collection followed by a single cour se of high dose chemotherapy and stem cell infusion with G-CSF stimulated m arrow recovery leads to rapid, reliable engraftment with low toxicity and p romising outcome in women with responding metastatic breast cancer.