Prognostic significance of the detection of tumour cells in peripheral blood stem cell collections in stage II and III breast cancer patients treated with high-dose therapy.

The purpose of this study was to evaluate the incidence and extent of tumour cell contamination in bone marrow specimens and stem cell collections from 34 breast cancer patients undergoing high-dose therapy as adjuvant treatment, and to determine the prognostic significance for the clinical outcome. Tumour cell contamination was evaluated by flow cytometry using a double-colour test and an anti- Pan cytokeratin (CK) antibody. Two out of 34 (6%) baseline bone marrow specimens, none of seven marrow harvests and nine out of 32 aphereses (28%) mobilised from seven out of 27 patients (26%) contained CK+ cells. Tumour contamination was more frequent in patients with 10 or more involved lymph nodes and in those who received a shorter course of adjuvant chemotherapy before mobilisation. At a median follow-up of 43 months, 24 patients are in complete remission, whereas 10 patients experienced recurrence. Out of the 10 patients who relapsed, five (50%) had CK+ peripheral blood stem cell (PBSC) collections, whereas disease recurrence was seen in only two out of 24 (8%) patients who received CK- products (P=0.02). Moreover, CK+ PBSC collections were associated with a significantly shorter event-free survival and overall survival. CK+ collection is an unfavourable prognostic factor for patients treated with high-dose therapy. Whether the negative impact on clinical outcome depends on reinfusion of tumour cells or whether it simply indicates a larger disease extension is still unclear.