Occult tumor contamination of hematopoietic stem-cell products does not affect clinical outcome of autologous transplantation in patients with metastatic breast cancer.

To determine whether occult tumor contamination of autologous bone marrow or peripheral-blood progenitor cells (PBPC) influences clinical outcome after high-dose chemotherapy in patients with stage IV breast cancer. We used an immunocytochemical assay capable of detecting one tumor cell in 5 x 10(5) hematopoietic cells to analyze bone marrow and/or PBPC collections obtained from 57 consecutive women with chemotherapy-sensitive metastatic breast cancer who received high-dose chemotherapy. The influence of occult tumor on time to progression, overall survival, and first site of recurrence (old or new) was studied. Twenty-three of 57 (40%) patients received bone marrow (n=6) or peripheral-blood progenitor collections (n=17) that contained microscopic cancer. Median time to progression and overall survival were 9 and 22 months in patients who did not receive infused tumor cells, compared with 10 and 24 months, respectively, in those who received occult tumor (P=not significant [NS]). Worse survival, but not time to progression, was observed in six patients who received > or = 2/100,000 tumor cells. Regardless of whether occult tumor was infused, the majority of relapses occurred in prior, rather than new sites of disease. Three patients who received stem-cell products contaminated by microscopic breast cancer remain free from progression at 21+, 47+, and 52+ months. Microscopic tumor was frequently detected by immunocytochemistry in hematopoietic stem-cell products, but did not predict for inferior treatment outcome in this cohort of patients with metastatic breast cancer. Quantitative information regarding infused tumor burden may have prognostic significance.