Evaluation of thrombopoiesis kinetics by measurement of reticulated platelets and CD34(+) cell subsets in patients with solid tumors following high dose chemotherapy and autologous peripheral blood progenitor cell support.

BACKGROUND AND OBJECTIVES The transplantation of mobilised peripheral progenitor cells has resulted in shortening of neutrophil and platelet engrafment times following high-dose chemotherapy. Since reticulated platelet percentage (PR%) has been established as a measure of bone marrow platelet production, we performed this type of analysis on the thrombopoietic compartment during transplant-related chemotherapy. DESIGN AND METHODS Kinetics of thrombopoiesis of 19 patients with solid tumors undergoing a single or double autologous peripheral blood progenitor cell transplant was characterized by evaluating the level of RP. The correlation between CD34(+) cell subsets and the time of highest percentage of RP was also evaluated. RESULTS The percentage of RP increases since day +8 after single transplant reaching the peak (3.4%) at day +10. In the group of patients receiving double transplant, the RP value of peak observed after second transplant is not significantly different from that one observed after the first transplant (3 vs 3.7%). In a subgroup of patients both the number of CD34(+) cells/Kg infused and the percentage of CD34(+) CD61(+) cell subsets correlate with the day of RP peak. INTERPRETATION AND CONCLUSIONS These results suggest that RP measurement is an early indicator of engraftment. Additionally, the observation that RP percentage is high at the time of platelet transfusion in 13 out of 20 cases of transfusions (the 7 cases with low RP value being transfused during the period of obligate thrombocytopenia) suggests that the evaluation of this parameter, together with the platelet count, can be used to monitor the need for platelet transfusion.