Background: Several studies have shown that Pegfilgrastim, the long acting agent of rh-GCSF, is as effective as Filgrastim in children undergoing cytotoxic chemotherapy by reducing the duration of neutropenia without increased adverse events as bone pain and headache. Recent studies in adults have shown that Pegfilgrastim is also effective to mobilize CD 34+ stem cells. In contrast to Filgrastim studies showed a reduction of time to reach the peripheral blood CD 34+ cell peak, resulting in earlier performance of leukapheresis. Although the use of Pegfilgrastim in children after conventional chemotherapy is established, only few data have been published yet describing the ability to mobilize CD 34+ stem cells. The aim of the study was to compare the efficacy of Pegfilgrastim versus Filgrastim for CD 34+ stem cell mobilization in children and adolescents.

Methods: Patients admitted after 2006 were stimulated with Pegfilgrastim on day 4 following a chemotherapy course of the according treatment protocol followed by peripheral stem-cell-apheresis. Filgrastim was added when CD 34 + stem cells did not reach 15/μl between day 15 to 20. Patients were compared to historical controls (2002–2005) stimulated with conventional daily Filgrastim.

Results: 3 groups of patients were compared: Group 1 (historical group): 6 patients with Ewing’s Sarcoma undergoing chemotherapy according to the EURO-EWING protocol receiving Filgrastim 10–20 μg/kg (median 11 μg/kg) underwent a median of 3,8 peripheral stem cell collections (PSCC) between day 12–24 (median 15,4). A median of 16,9 CD 34+ stem cells/kg BW were collected. Group 2: 3 Patients with Ewing’s Sarcoma admitted after 2006 undergoing chemotherapy according to the EURO-EWING protocol received only Pegfilgrastim 100–200 μg/kg (median 166 μg/kg). 3 PSCC were performed between day 11–13 (median 12) and a median of 24,3 CD 34+ stem cells/kg BW were collected. Group 3: 5 Patients suffering from recurrent neoplasm [B-NHL (n=1), medulloblastoma (n=1), ependymoma (n=1) and germ cell tumor (n=2)]. Chemotherapy was performed according to relapse protocols followed by Pegfilgrastim 150–200μg/kg (median 188 μg/kg), however 2 patients needed further cytokine stimulation with Filgrastim 10–15μg/kg (median 12,5 μg/kg) combined with stem cell factor. A median of 3,2 PSCC was performed between day 8–30 (median 17). A median of 11,9 CD 34+ stem cells/kg BW were collected.

Discussion: Our data show that stem cell mobilisation with Pegfilgrastim seems to produce earlier CD34+ peaks and better CD34+ yields than Filgrastim in children when performed during primary or without previous long lasting chemotherapy. However patients with previous long lasting chemotherapy might need additional mobilisation therapy with Filgrastim and/or stem cell factor.

Disclosures: No relevant conflicts of interest to declare.

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