Tumor contamination of hematopoietic stem cell grafts may influence the outcome of
breast cancer patients treated with high-dose
chemotherapy. The goals of this study were: (a) to evaluate the prevalence of
tumor contamination of bone marrow (BM) harvests in patients responding to systemic
chemotherapy; (b) to evaluate reduction of BM
tumor contamination by ex vivo purging with
4-hydroperoxycyclophosphamide (4HC); and (c) to compare the
tumor contamination of peripheral blood progenitor cell collections and BM in advanced-stage
breast cancer patients designated for peripheral blood progenitor cell infusion. We evaluated pre- and post-4HC purge BM specimens from 20 patients for
tumor contamination using immunocytochemistry and for in vitro growth potential of
tumor cells using a
tumor cell clonogenic assay. Pre-4HC purge BM specimens from 15 of 20 (75%) patients were immunocytochemistry and
tumor cell clonogenic assay negative. The remaining 5 BM specimens were immunocytochemistry positive, but only 3 of 5 specimens were
tumor cell clonogenic assay positive. In vitro
tumor colony growth was not observed in any post-4HC purge BM specimens. We also evaluated nine patients with bone or BM
metastases from the start of
induction chemotherapy. We found less
tumor involvement of peripheral blood progenitor cell collections than of simultaneously obtained bone marrow aspirates. We conclude that bone marrow
micrometastases occur with low frequency in women with
chemotherapy-sensitive
breast cancer and that ex vivo purging with 4HC may render
tumor cells nonviable.