Bone Marrow Transplantation (2001) 28, 563–571 2001 Nature Publishing Group All rights reserved 0268–3369/01 $15.00 www.nature.com/bmt Mobilization Topotecan–filgrastim combination is an effective regimen for mobilizing peripheral blood stem cells E-JA Yeoh1,7, JM Cunningham1,5,GCYee6, D Hunt2, JA Houston1, SL Richardson1, CF Stewart3, PJ Houghton4, LC Bowman1,5 and AJ Gajjar1,5 Departments of 1Hematology-Oncology, 2Biostatistics, 3Pharmaceutical Sciences, 4Molecular Pharmacology, St Jude Children’s Research Hospital, Memphis, TN, USA; 5Department of Pediatrics, College of Medicine, University of Tennessee Health Sciences Center, Memphis, TN, USA; 6Department of Pharmacy Practice, College of Pharmacy, University of Nebraska Medical Center, Omaha, NE, USA; and 7Department of Pediatrics, National University of Singapore, Singapore Summary: malignancies.1–5 Improvements in supportive care and increasing experience with stem-cell rescue after myeloabl- We compared the efficacy, toxicity, and cost of topote- ative chemotherapy have reduced the morbidity of high- can–filgrastim and filgrastim alone for mobilizing dose chemotherapy, and this reduction in morbidity has peripheral blood stem cells (PBSCs) in 24 consecutive made such treatment applicable to a wide spectrum of pediatric patients with newly diagnosed medulloblas- diseases.6 Peripheral blood stem cells (PBSCs) are increas- toma. PBSCs were mobilized with an upfront window of ingly used for rescue because of their engraftment charac- topotecan–filgrastim for 11 high-risk patients (residual teristics and the ease with which they can be collected.7,8 tumor у1.5 cm2 after resection; metastases limited to Stem cells are usually mobilized into the peripheral neuraxis) and with filgrastim alone for 13 average-risk blood in one of three ways: with cytokine therapy alone, patients. All patients subsequently underwent craniospi- with myelosuppressive chemotherapy alone or with a com- nal irradiation and four courses of high-dose chemo- bination of both.9 The present standard of care uses filgras- therapy with stem cell rescue. Target yields of CD34+ tim (G-CSF) or sargramostim (GM-CSF) to mobilize -cells (у8 ؋ 106/kg) were obtained with only one apher- PBSCs, but these agents may not mobilize a sufficient num esis procedure for each of the 11 patients treated with ber of stem cells in as many as 67% of patients.10–12 For topotecan–filgrastim, but with a mean of 2.3 apheresis these patients, alternative mobilization regimens are procedures for only six (46%) of the 13 patients treated needed.10,13 The choice of regimen to enhance mobilization, with filgrastim alone (P = 0.0059). The median peak and particularly for children, is important because of the poten- median total yield of CD34+ cells were six-fold higher tial increased toxicity of chemotherapy-based mobilization for the topotecan–filgrastim group (328/␮l and 21.5 ؋ and because of the need for additional apheresis procedures 106/kg, respectively) than for the filgrastim group (54/␮l and marrow backups required with regimens using cyto- and 3.7 ؋ 106/kg, respectively). Mean times to neutro- kines alone. Therefore, it is imperative to evaluate the phil and platelet engraftment were similar. Myelosup- economic and therapeutic impact of any new mobilizing pression was the only grade 4 toxicity associated with regimen to determine its usefulness.14 topotecan–filgrastim mobilization and lasted a median Topotecan, a new topoisomerase I inhibitor with promi- of 5 days. Compared with filgrastim mobilization, topo- nent activity15 against many malignancies in pediatric and tecan–filgrastim mobilization resulted in a mean cost adult patients, is being evaluated in several new treatment saving of $3966 per patient. Topotecan–filgrastim is an regimens for various tumors.16–19 Our aim was to compare efficacious, minimally toxic, and cost-saving combi- the efficacy, toxicity, and relative costs of intravenously nation for PBSC mobilization. Bone Marrow Transplan- administered topotecan and filgrastim and of filgrastim tation (2001) 28, 563–571. alone in mobilizing PBSCs. This retrospective obser- Keywords: topotecan; peripheral blood stem cell; filgra- vational study was part of our institutional medullo- stim; high-dose chemotherapy; medulloblastoma; children blastoma/primitive neuroectodermal tumor (PNET) protocol. High-dose chemotherapy is increasingly used as front-line Patients and methods therapy for adult and pediatric patients with high-risk Patients Correspondence: Dr A Gajjar, Department of Hematology-Oncology (Room 6024), St Jude Children’s Research Hospital, 332 North Lauder- Patient eligibility criteria and definitions of average-risk 20 dale, Memphis, TN 38105–2794, USA and high-risk disease have been previously reported. The Received and accepted 18 July 2001 protocol was approved by the Institutional Review Board. Topotecan as a PBSC mobilizer E-JA Yeoh et al 564 Signed informed consent was obtained from parents or anti-CD34 monoclonal antibody (CD34-PE; BD legal guardians, as appropriate, before protocol therapy Biosciences), PerCP-labeled anti-CD45 antibody (CD45- was initiated. PerCP; BD Biosciences), and fluorescein isothiocyanate (FITC)-labeled anti-CD3 antibody (CD3-FITC; DAKO ␮ Study design Corporation, Carpinteria, CA, USA). Briefly, 50 lof diluted whole blood from each patient was mixed with 50 Patients with average-risk disease received intravenously ␮l of Dulbecco’s phosphate-buffered saline (BioWhittaker, (i.v.) administered filgrastim (Neupogen; Amgen, Thousand Walkersville, MD, USA), 1% human serum albumin, 0.1% Oaks, CA, USA) at a dose of 10 ␮g/kg daily21 until the sodium azide, and 10 ␮l of each antiserum (CD45-PerCP, absolute peripheral CD34+ cell count was at least 20/␮l. CD3-FITC, and CD34-PE). A control sample was analyzed PBSC harvesting then began and continued until the target with PE-labeled and FITC-labeled mouse IgG1 and CD45- yield of 8 ϫ 106 CD34+ cells/kg was obtained or until the PerCP. The mixtures were incubated in the dark at room absolute peripheral CD34+ cell count dropped below 20/␮l. temperature for 10 min and erythrocytes were subsequently Because of patient tolerance, the maximum number of aph- lysed with FACSLyse (BD Biosciences). Each sample was eresis procedures per patient was prospectively limited to then washed twice before 105 to 106 cells from each sample three. The patients subsequently underwent craniospinal were analyzed. irradiation over a period of 6 weeks, followed by a 6-week rest period. Patients then received four courses of high-dose Peripheral and marrow stem-cell harvest chemotherapy; each course was followed by reinfusion of at least 2 ϫ 106 autologous CD34+ cells per kg (Figure 1).22 PBSCs were harvested by using COBE Spectra (COBE, Patients with high-risk disease were given two cycles of Lakewood, CO, USA) apheresis machines. The total blood outpatient chemotherapy consisting of topotecan (5.5 volume (each blood volume was assumed to be 75 ml/kg mg/m2 daily as an i.v. infusion for 5 days every 21 days). of body weight) from each patient was processed three The day 1 topotecan dosage was 5.5 mg/m2, and subsequent times. On the day before PBSC harvest (ie the day on which doses were adjusted to maintain the target topotecan lactone the absolute peripheral CD34+ cell count was predicted to area under the plasma concentration-time curve (AUC) be greater than 20/␮l), a 5-French single-lumen central between 120 and 160 ng/ml/h. Twenty-four hours after the venous catheter (Cook, Bloomington, IN, USA) was last dose of topotecan, patients received i.v. filgrastim (10 inserted into the femoral vein of those patients without ␮g/kg per day) until the absolute peripheral CD34+ cell adequate peripheral venous access. The catheter was left in concentration was at least 20/␮l. Daily peripheral CD34+ place for the duration of apheresis and was removed after cell counts began on day 1 of filgrastim administration for the last apheresis procedure of the mobilization cycle. the first four patients in the topotecan–filgrastim mobiliz- Anticoagulation was achieved by adding acid-citrate- ation. Because the initial four patients who received topote- dextrose (ACD); the ratio of blood to ACD was 15:1. Blood can and filgrastim did not have measurable CD34+ cell flow was dependent on the draw line and did not exceed counts before day 4, the CD34+ cell counts for the remain- 15 ml/kg/min. The maximum rate of ACD was 1 ing patients were obtained when the leukocyte count ml/kg/min. No calcium replacement was given unless exceeded 1.0 ϫ 109/l or after day 3 of filgrastim adminis- symptomatic hypocalcemia occurred. tration. Guidelines for harvesting PBSCs were similar to those of the average-risk group. After PBSCs were col- Patient monitoring lected, the patients in the high-risk group were given a second course of topotecan followed by craniospinal During mobilization, complete blood counts (CBCs) and irradiation, a 6-week rest period, and four courses of high- absolute peripheral blood CD34+ cell counts were perfor- dose chemotherapy and PBSC rescue that were identical to med daily. Patients were monitored for signs of toxicity as those given to patients with average-risk disease (Figure 1). defined by Version 2 of National Cancer Institute (NCI) Although the chemotherapy regimen was not myeloabl- common toxicity criteria. Blood chemistry values were ative, PBSC rescue was performed after each course of evaluated twice a week or when clinically appropriate. chemotherapy, so that the dose intensity of the regimen 20 could be maintained. Storage and reinfusion of stem cells In either group, if the target cell yield was not obtained, bone marrow was harvested from the iliac bone or PBSC Stem cells underwent no manipulation and were stored in a harvest was repeated, either before or after radiotherapy. final concentration of 10% dimethyl sulfoxide diluted with The target dose of marrow cells required for each cycle autologous plasma or 5% human serum albumin according of high-dose chemotherapy was 1 ϫ 108 nucleated cells to standard procedures.