Discussion
The Peg-GCSF has a longer half-life requiring a one-time administration as compared to conventional recombinant human GCSF which has a short half-life and hence requiring daily administration. This makes it more tolerable and acceptable for children (7-9). Peg-GCSF also provides a sustained drug level as compared to pulse like levels with GCSF which is more effective for PBSC mobilization (9).
Most of the experience with Peg-GCSF comes from its use for prophylaxis and treatment of chemotherapy associated neutropenia in children and adults as well as for PBSC mobilization in adults. There is paucity of literature of successful use of Peg-GCSF and its appropriate dosing for PBSC mobilization in children. From the meagre published data, we can draw conclusion that it is non-inferior to conventional GCSF with regard to efficacy and safety (1,6,15,16). We have described here our experience of PBSC mobilization with Peg-GCSF in 9 children. Our patients received chemotherapy followed by Peg-GCSF and we found in our cohort a fairly uniform and predictable time to CD34 peak from start of chemotherapy and from the administration of Peg-GCSF. Also, we were able to harvest the desired CD34 stem cell dose in single harvest procedure for all our patients including the ones with relapsed malignancies who were heavily pretreated and hence deemed poor mobilisers. None of our patients had any major adverse event. All our patients who received autologous HSCT had a brisk and robust engraftment.
Fritsch et al. have reported a similar successful and safe harvest experience among their patient cohort which comprised of first time diagnosed solid tumor patients as well as relapsed cases. Also, no other adverse events except leukocytosis had been observed in all their patients (1). The side effect of leukocytosis was lower in those who received Peg-GCSF because Peg-GCSF has a predominant neutrophil mediated elimination and hence its clearance is self-regulating (1,7). Dallorso et al found a success rate of ~77% for PBSC mobilization with single dose of 100mcg/kg of Peg-GCSF. They also found that CD34 cell levels more than 20/microliter were first observed in the peripheral blood at a median of 6 days after Peg-GCSF administration and they remained sustained above 20/microliter for a median of 6 days. This points to another appealing aspect of Peg-GCSF that it provides a wider temporal window for planning harvest in case the peak is apparently likely to coincide with a holiday (15). Merlin et al reported a success of 60% with peg-GCSF. Target dose of 5 million/kg stem cells could be collected with a single apheresis procedure in only 16 out of 26 children despite using higher dose of peg-GCSF 300 microgram/kg (16). In our cohort, PBSC could be harvested successfully in 100% of patients with a single apheresis procedure. We used lower dose of peg-GCSF 100 microgram/kg in all our patients. Lowest dose of stem cell collected in our cohort was 4 million/kg.
Peg-GCSF can circumvent the concerns of daily painful GCSF injections thereby improving the compliance and making the entire experience of autologous hematopoietic stem cell harvest more tolerable for children. Our experience highlights that its feasible and safe to mobilise PBSC with peg-GCSF in children with cancer.
Disclosure – All authors have nothing to declare. All authors have contributed to this manuscript. DT wrote manuscript, AT collected data, SP-Collected data, GA-collected data, RK-reviewed literature, NR- reviewed literature, SY-wrote manuscript