The Optimal Timing for Stem Cell Collection After Induction Therapy for Patients with Multiple Myeloma

High dose chemotherapy and stem cell transplant remains an integral part of the therapy for Multiple Myeloma patients under age of 70. The collection of sufficient number of stem cells for one or more transplant is however sometimes a challenge. Moreover, the optimal timing for stem cell collection after induction chemotherapies is controversial. The standard recommendation is for stem cell collection after 4–6 cycles of non-alkylator regimen, however studies to support this practice are limited.

We conducted a retrospective analysis of 366 patients who were diagnosed with multiple myeloma and mobilized at the Hospital of University of Pennsylvania between January 2002 and December 2008. Patients who did not meet the initial inclusion criteria were those who had induction regimens containing an alkalytor agent or whose regimens were not well documented and were excluded from futher analysis (85). Every 4 cycles of any non-alkalytor agent was considered to be one treatment session for the purpose of this analysis. 245 patients received 1 or 2 treatment sessions and 36 received > 2. All patients were mobilized with either Cyclophosphamide/G-CSF (CY/G-CSF), Plerixafor/G-CSF (AMD/G-CSF), or G-CSF alone.

The mean number of collected CD 34+ cells (CD 34+) was 9.22 × 10⁶ CD34+/Kg in the patients who received 1 or 2 sessions and 6.87 × 110⁶ CD34+/Kg in the patients who received > 2 sessions (P= 0.005). The number of the patients who collected > 6 × 10⁶ CD34+/Kg was 63%(153/246), 53%(19/36) respectively, (p= 0.005). The patients who mobilized with either CY/G-CSF or AMD/G-CSF collected higher number of CD34+ than the patients mobilized with G-CSF alone in both groups. (Table 1, 2.)

The mean number of collected stem cells was 7.14 × 10⁶ CD34+/Kg in the patients who received more than 2 sessions of different regimens and 6.26 × 10⁶ CD34+/Kg in the patients who received > 2 sessions of the same regimen.

The patients who mobilized after fewer than 8 cycles of non-alkylator agents (2 sessions) collected a higher number of CD 34+ than those with greater than 8 cycles. CY/G-CSF or AMD/G-CSF are similar and superior to G-CSF alone in the more heavily treated patients. The patients who received multiple sessions of the same regimen have similar outcome compared to those who received multiple different regimens suggesting that the duration of the treatment may impact stem cell collection more than the content of the regimen. Prospective studies in this regards are warranted.

No relevant conflicts of interest to declare.