Incidence of tumor-cell contamination in leukapheresis products of breast cancer patients mobilized with stem cell factor and granulocyte colony-stimulating factor (G-CSF) or with G-CSF alone

We have assessed tumor contamination of peripheral blood progenitor cells ( PBPC) in 203 high-risk breast cancer patients who were prospectively random ized to mobilization with stem cell factor (SCF) plus granulocyte colony-st imulating factor (G-CSF) versus G-CSF alone. The patients then received hig h-dose cyclophosphamide, cisplatin, and carmustine (BCNU) with PBPC support . One bone marrow aspirate obtained before treatment, one whole blood speci men obtained before cytokine infusion, and one to five leukapheresis produc ts were tested for the presence of tumor cells by an alkaline phosphatase i mmunocytochemical technique with a targeted sensitivity of 1.7 tumor cells per 10(6) hematopoietic cells. Tumor cells were detected in the bone marrow , peripheral blood, and/or PBPC of 21 patients (10%). In 14 patients, bone marrow specimens were tumor-positive; in seven patients, premobilization wh ole blood specimens were tumor-positive, and in eight patients, leukapheres is products were tumor-positive. In five patients, repetitive or multiple s pecimens were tumor-positive, and in three cases, marrow, peripheral blood, and PBPC products were all tumor-positive. Nine of the patients in whom tu mor cells were found in marrow or peripheral blood were clinical stage II t o III and 12 were clinical stage IV. Nine of the tumor-positive patients we re in the SCF + G-CSF arm and 12 were in the G-CSF arm. Tumor cells were de tected in leukapheresis products of eight patients: three in the G-CSF + SC F arm and five in the G-CSF arm. We conclude that detectable tumor-cell con tamination of bone marrow, peripheral blood, and/or PBPC occurred in approx imately 10% of patients in this trial and was observed in stage II to III p atients, as well as in stage IV patients. No significant difference could b e found in the rate of PBPC tumor-cell contamination between patients who r eceived SCF + G-CSF compared with those who received G-CSF alone. Neither m obilization regimen was found to increase the rate of tumor cell contaminat ion when control premobilization blood samples were compared with leukapher esis products. (C) 1999 by The American Society of Hematology.