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Chapter 5: Myeloma
Table 2. Descriptive statistic of tumor cell content and stem cell yield
n Mean Minimum Maximum SD SE
MNCofLP 29 41.3 4.5 117.6 30.38 5.64
Tumor cells (%) 30 0.04 0.0 0.71 0.13 0.024
Number of tumor cells (X10 6
) 29 17.91 0.0 273 51.47 9.56
CD34 +
stem cells (%) 30 2.05 0.1 9.72 2.15 0.39
Number of CD34 +
cells (X10 6
) 29 816.71 9.20 3591 987.72 183.42
SD, standard deviation; SE, standard error.
Statistical analysis
Correlating the kind and the number of pretreatment cycles with the tumor cell
load in LP 1, a significant reduction in the number of tumor cells could be observed
as a consequence of the treatment with cycles of alkylating agents at all (Z^O.035).
The corresponding regression curve is shown in Fig. 2. Focusing on the inclusion
of alkylating agents in the last three treatment cycles before mobilization
confirmed this significant effect on lowering the tumor cell numbers in LP 1
(P=0.016). Determination of the impact of both parameters on the stem cell yield
revealed a concomitant significant reduction in the stem cell yield (P=0.00004;
F=0.0004) (Fig. 3).
DISCUSSION
Tumor cell contamination in autologous grafts as a possible source of relapse is
still a major concern in autologous transplantation. For MM, a borderline significance
for the number of plasma cells autografted in predicting relapse-free
survival has been demonstrated. 17
Purging procedures have been proposed for
tumor cell reduction. 910
Whether the pretreatment protocols used have an influence
on the tumor load of the harvests has been studied recently. Cremer et al. 18
demonstrated that chemotherapy-containing mobilization regimens were able to
significantly lower the tumor cell number in leukapheresis products compared with
the use of growth factor alone. Omede et al. 11
presented the possibility of reducing
tumor cell contamination in LP by repeated cytotoxic chemotherapy courses before
PBSC collection. Whether different conventional pretreatment regimens also have
an effect on the number of tumor cells in apheresis products is not yet determined.
We described here for the first time that pretreatment with alkylating agents in MM
resulted in lower tumor cell numbers in aphereses harvested after chemotherapy
and G-CSF mobilization compared with the pretreatment with VA[I]D. This effect
was after administration of alkylating agents in the last three cycles of conventional
chemotherapy before mobilization regimens. Our study also confirmed the adverse