Factors Influencing Peripheral Blood Progenitor Cell Yield After 2^nd Mobilization With G-CSF In Allogeneic Donors

2^nd collection of Peripheral Blood Progenitor Cells (PBPC) from the same donor is increasingly required for the treatment of complications after allogeneic transplantation, but information regarding the efficacy of this procedure is still limited.

Within our program 212 allogeneic donors underwent a 2^nd cycle of G-CSF-application and PBPC leukapheresis between 1996 and 2012. Demographical data and details of donation are shown in table 1. G-CSF (lenograstim) was administered at a median daily dose of 7.5µg/kg for 4.5d; leukapheresis was performed on day 5 and 6, if necessary. Peripheral CD 34⁺ counts and leukapheresis yields after both mobilization cycles were compared. The influence of age, sex, BMI, G-CSF schedule and the interval between the donations on the efficacy of the 2^nd PBPC mobilization were analyzed, too.

Median CD 34⁺ counts in peripheral blood were 53.2/µl at day 5 of 1^st mobilization compared to 49.5/µl at day 5 of 2^nd mobilization. Between 1^st and 2^nd donation, the median yield of CD 34⁺ cells/kg recipient b.w. decreased from 7.3 x 106 to 6.6 x 106 (p = 0.026, see table 2). The number of aphereses necessary in both donation episodes did not differ in the majority of donors (n=175; 82.5%). A strong correlation was observed between the amount of CD 34⁺ cells per recipient b.w. after the 1^st and 2^nd PBPC donation (r=0.89). The majority (65.4%, n=17) of donors with poor mobilization (<3 x 106 CD 34⁺ cells/kg recipient b.w.) after the 1^st leukapheresis reached similar low CD 34⁺ counts after the 2^nd mobilization. The interval between both mobilization cycles did not affect the results of the 2^nd donation. According to an adjusted model, the other variables (age, sex, BMI and G-CSF-schedule) had no additional influence on mobilization efficacy in the 2^nd cycle of G-CSF application.

In the largest group of healthy donors reported so far, we could demonstrate a slight reduction (about 10%) of PBPC yield after the 2^nd mobilization that might not be clinically significant. Demographic variables affected the results of both mobilization episodes in the same way and the interval between them was of no significance. Our data support the assumption, that stem cell mobilization is probably determined by genetic factors and the outcome of a 2^nd donation can easily be predicted by the results of the 1^st one.

No relevant conflicts of interest to declare.