ORIGINAL ARTICLE Prospective single-arm study of pegfilgrastim activity and safety in children with poor-risk malignant tumours receiving chemotherapy S Dallorso 1 , M Berger 2 , I Caviglia 1 , T Emanueli 3 , M Faraci 1 , L Scarso 4 , F Fagioli 2 and R Haupt 5 1 Paediatric Haematology-Oncology Department, G Gaslini Children’s Hospital, Genoa, Italy; 2 Paediatric Haematology-Oncology Unit, Regina Margherita Hospital, Turin, Italy; 3 Pharmacy Department, G Gaslini Children’s Hospital, Genoa, Italy; 4 Blood Bank, G Gaslini Children’s Hospital, Genoa, Italy and 5 Epidemiology and Biostatistics Section, Scientific Directorate, G Gaslini Children’s Hospital, Genoa, Italy The objective of this study was to assess the efficacy of an injection of 100 lg/kg of pegfilgrastim in haematopoietic recovery and mobilization in children following 32 courses of chemotherapy. End points were duration of neutro- paenia, myeloid recovery and PBMC collection. Neutro- paenia lasted a mean of 4.7 days ( ± 2.13 days). Myeloid recovery occurred at a median of 10 days (inter quartile range (IQR) 8–11). Febrile neutropaenia complicated 13 courses (40.6%). Mobilization was observed in 20 out of 26 assessable courses (76.9%). The rise in CD34 þ cells occurred at a median of 6 days (IQR 4–7) after PEG and remained 420 per ll for 6 days (IQR 4–8), with a median value of 80 per ll (IQR 48–170.5). The median CD34 þ cell peak was 165 per ll (IQR 82.5–331), 9 days (range 6–14) after PEG. PBMC were collected on average at day þ 5( þ 4 to þ 9) after PEG. In 93.3% of collections, at least 3  10 6 per kg CD34 þ cells were collected through a single apheresis. Myeloid recovery occurred in all cases within 15 days, without concomitant thrombocytopaenia. The incidence of primary febrile episodes is in line with data in the literature and with our own historical experience. A long-lasting period of circulating CD34 þ cells allowed for more accurate scheduling of apheresis. Bone Marrow Transplantation (2008) 42, 507–513; doi:10.1038/bmt.2008.206; published online 21 July 2008 Keywords: pegfilgrastim; neutropaenia; children; PBMC apheresis Introduction Chemotherapy-induced neutropaenia is important in in- creasing the risk of infection in children with malignant diseases. The risk of infection is related to the severity and duration of neutropaenia which, if complicated by fever, often requires the administration of antibiotics and hospital admission. 1 Furthermore, it can also compromise the ability to deliver the full dose of chemotherapy on schedule. 2 Myeloid growth factors, mostly G-CSF (filgrastim), are used the world over to decrease the period of neutropaenia between courses of chemotherapy as well as to mobilize transplantable haematopoietic progenitor cells in the blood. 3 G-CSF has a short half-life due to its almost complete renal clearance, thus injections must be given daily to achieve full clinical benefits such as PBMC mobilization or haematological recovery. Pegylation (that is, the covalent binding of a 20kDa PEG molecule to the N-terminal methionine residue of filgrastim) led to a new form of the drug (Pegfilgrastim; Amgen Inc., Thousand Oaks, CS, USA), which has shown a prolonged half-life and sustained serum levels, thanks to the neutrophil- mediated clearance dominant mechanism. 4,5 Pegfilgrastim (PEG) has also shown comparable safety and efficacy to the non-pegylated molecule. 6,7 However, most of these studies were carried out on adults and little information is available on children. The aim of this study was to evaluate the activity and safety of PEG in enhancing both neutrophil recovery and PBMC mobilization after chemotherapy in children with cancer. Patients and methods Eligibility criteria This prospective, single-arm study was carried out between August 2005 and October 2006, at two Italian paediatric institutions (Gaslini Children’s Hospital, Genoa and Regina Margherita Hospital, Turin). The aim was to evaluate the efficacy and tolerability of PEG administration in children with cancer. Children (o18 years of age) with cancer and a Lansky (or Karnofsky if older than 16 years) score 450, receiving aggressive front-line or salvage myelosuppressive chemo- therapy according to various national or international protocols that called for G-CSF stimulation in the postchemotherapy phase, were eligible for this study. Received 2 April 2008; revised 27 May 2008; accepted 30 May 2008; published online 21 July 2008 Correspondence: Dr S Dallorso, Paediatric Haematology-Oncology Department, G Gaslini Children’s Hospital, Largo Gaslini, 5, 16147 Genoa, Italy. E-mail: sandrodallorso@ospedale-gaslini.ge.it Bone Marrow Transplantation (2008) 42, 507–513 & 2008 Macmillan Publishers Limited All rights reserved 0268-3369/08 $32.00 www.nature.com/bmt