AUTOLOGOUS PERIPHERAL-BLOOD PRECURSOR CEL L TRANSPLANTATION AFTER CD34 SELECTION

Peripheral blood is increasingly used instead of bone marrow as a sour ce of hemopoietic precursor cells for transplantation. The optimal tec hnique still needs to be defined. Selection of CD34(+) cells in transp lant material may be of benefit in allogeneic and autologous periphera l blood precursor cell transplantation (PBPCT), since it allows elimin ation of unwanted CD34-negative cells, such as T-cells and contaminati ng tumor cells. We have evaluated the feasibility of CD34 selection in PB transplants and studied hemopoietic reconstitution after autologou s transplantation of CD34 selected precursor cells. Between August 199 4 and June 1995 CD34 selection was performed on 12 transplants for 9 p atients with malignant disease (non-Hodgkin lymphoma [n = 5]; Ewing sa rcoma [n = 1]; chronic lymphocytic leukemia [n = 1]; breast cancer [n = 1]; multiple myeloma [n = 1]). PBPC were collected with a Fenwall CS 3000 harvester after stimulation with G-CSE. For selection of CD34(+) cells the Ceprate LC34 system (CellPro(TM)) was used. A median CD34 p urity of 73% (range 40-94%) was achieved. The median number of CD34 po sitive cells per transplant was 4.8x10(6)/kg body weight (range 0.7-15 .8). The median number of colony forming cells per transplant was 31x1 0(4)/kg body weight (range 1.5-131.3). For autologous PBPCT the minima l number of CD34 positive cells required in the transplantate was arbi trarily set at 1.0x10(6)/kg body weight. This number was achieved in 1 0 of the 12 transplants. The median loss of CD34(+) cells during selec tion was 1.5x10(6)/kg body weight (range 0.2-6.4). In 2 patients the t otal number was reduced to below the critical value of 1.0x10(6)/kg. 7 of the 9 patients received the CD34 selected transplant after intensi ve chemotherapy and irradiation. The median follow-up time after PBPCT was 196 days (range 62-278). All 7 patients are now alive and with no rmal hemopoietic function. A granulocyte count above 0.5x10(9)/l and a platelet count above 20x10(9)/l was achieved on day 14 (median), and on day 19 after PBPCT. We conclude that CD34 selection is technically feasible and that CD34 selected cells can be used for PBPCT. The proce dure is time consuming and expensive; it requires complex organization at laboratory level, and the benefit of CD34 selection with regard to T-cell depletion and tumor purging still needs to be proven. However, CD34(+) selection is likely to open new perspectives in transplantati on medicine.