Influence of Preharvest Tumor Cell Contamination in Bone Marrow or Blood Does Not Predict Resultant Tumor Cell Contamination of Granulocyte Colony-Stimulating Factor Mobilized Stem Cells

Micrometastases in apheresis products predict shorter progression-free and overall survival in patients with breast cancer undergoing high-dose chemotherapy (HDCT) and autologous blood stem cell transplantation (ABSCT)

The presence of cancer cells in autografts of breast cancer patients has been described to have prognostic value or directly lead to relapse. Previously, we demonstrated that apheresis products (APs) collected after induction chemotherapy have a significantly lower likelihood of tumor cell contamination. Here, we examine the prognostic value of micrometastases in autografts. Data from 83 patients with breast cancer treated with autologous blood stem cell transplantation were analyzed. Pan-cytokeratin-FITC conjugated antibodies were used to detect contaminating breast cancer cells in the APs. Progression and survival data analyzed on the basis of three or fewer cancer cells showed no significant differences in outcomes. Of the 83 patients, 11 had more than three cancer cells detectable in their APs. In total, 72 patients were shown to have less than three cells detectable. When patients with more than three cells were compared to patients with 0-3, we found statistically significant differences in progression-free survival. We also found a significant difference in overall survival (OS) between the two groups. No difference was observed in OS since the time of diagnosis. We conclude that patients with more than three contaminating cells in their APs have micrometastases and represent a poor prognosis group.

Disseminated breast cancer cells prior to and after high-dose therapy

Women with breast cancer in a distinct stage of disease can benefit from high-dose therapy (HDT) with autologous stem cell support; however, a significant number of these patients relapse despite this intensive treatment. This study investigates the persistence of malignancy on the single-cell level. A total of 194 data sets consisting of bone marrow and blood samples obtained prior to and after HDT and of aliquots of apheresis products were searched with immunocytochemistry and reverse transcriptase polymerase chain reaction (RT-PCR) for disseminated cancer cells. Presence of cancer cells in the marrow is frequent prior to and after HDT, but HDT reduces the amount of malignant cells in marrow significantly. In contrast, there was no effect on the number of circulating cancer cells. Reinfusion of contaminated apheresis products was surprisingly associated with a low number of malignant cells in bone marrow after HDT and vice versa. The impact of disseminated tumor cells in bone marrow, apheresis, and peripheral blood on disease-free survival after HDT could be investigated in a total of 165 samples. Surprisingly, neither the presence of tumor cells in marrow or blood nor in apheresis was associated with a bad prognosis in Kaplan-Meyer survival analysis. These results suggest that apheresis products and bone marrow should be regarded as different biological compartments for epithelial cancer cells. It can be concluded that complete elimination of disseminated cancer cells by HDT is not always possible. The theory of reinduction of metastatic breast cancer by accidentally reinfused contaminants is not supported by this study so far. However, further research is necessary to identify distinct cell populations with the potentially capacity to metastasize.