Therapy results in pediatric Hodgkin lymphoma - does less mean better? Experience from a single children's oncology center.

Therapy results in pediatric Hodgkin lymphoma reflect remarkable progress in pediatric oncology. In the last decade, relevant development of new therapeutic options for children with refractory or relapsed disease has been made. In this study, we retrospectively analyzed therapy results and risk factors in children treated in a single oncology center according to five therapeutic protocols. Data from 114 children treated by a single institution between 1997 and 2022 were analyzed. Classic Hodgkin lymphoma therapy results were divided into four therapeutic periods: 1997-2009, 2009-2014, 2014-2019, and 2019-2022. For nodular lymphocyte-predominant Hodgkin lymphoma, data from one therapeutic protocol was analyzed. For the entire group, the 5-year probability of overall survival was 93.5%. There were no statistically significant differences between therapeutic periods. The occurrence of B symptoms at diagnosis and incidence of relapse were risk factors for death (p = 0.018 and p < 0.001). Relapse occurred in 5 cases. The 5-year probability of relapse-free survival for the entire group was 95.2%, without significant differences between groups. Patients treated between 1997 and 2009 had over a sixfold higher risk for events, defined as primary progression, relapse, death, or incidence of secondary malignancies (OR = 6.25, p = 0.086). The 5-year probability of event-free survival for all patients was 91.3%. Five patients died, and the most common cause of death was relapse. Modern therapeutic protocols in pediatric Hodgkin lymphoma are marked by excellent outcomes. Patients with disease relapses have a notably high risk of death, and the development of new therapeutic options for this group remains one of the main goals of current trials.

Soluble Hemojuvelin and Ferritin: Potential Prognostic Markers in Pediatric Hematopoietic Cell Transplantation.

OBJECTIVE: Iron overload (IO) is a common and life-threatening complication resulting from the therapy of AL and HCT patients. This study aimed to evaluate the prognostic value of 12 serum biomarkers of iron metabolism in pediatric patients treated for AL or undergoing HCT. PATIENTS: Overall, 50 patients with AL after intensive treatment and 32 patients after HCT were prospectively included in the study. AL patients at diagnosis and healthy controls served as reference groups. METHODS: The impact of the following 12 serum iron metabolism parameters on the outcome of AL/HCT patients was analyzed: iron, transferrin (Tf), total iron-binding capacity (TIBC), ferritin, ferritin heavy chains (FTH1), ferritin light chains (FTL), hepcidin, soluble hemojuvelin (sHJV), soluble ferroportin-1 (sFPN1), erythroferrone (ERFE), erythropoietin (EPO), and soluble transferrin receptor (sTfR). RESULTS: With a median follow-up of 2.2 years, high levels of ferritin and low levels of sHJV had an adverse prognostic impact on OS and EFS in children after HCT. If these patients were combined with those with AL after intensive chemotherapy, the results were confirmed for OS and EFS both for ferritin and sHJV. CONCLUSIONS: Among the 12 analyzed serum parameters of iron metabolism, increased levels of ferritin and decreased levels of sHJV had an adverse prognostic impact on survival in children after HCT. More data are needed to clarify the relationship between ferritin, sHJV, and mortality of AL children after intensive chemotherapy, and more extensive prospective studies are required to prove sHJV predictivity.

Isolated central nervous system relapses in patients with high-risk neuroblastoma -clinical presentation and prognosis: experience of the Polish Paediatric Solid Tumours Study Group.

Although isolated central nervous system (CNS) relapses are rare, they may become a serious clinical problem in intensively treated patients with high-risk neuroblastoma (NBL). The aim of this study is the presentation and assessment of the incidence and clinical course of isolated CNS relapses. Retrospective analysis involved 848 NBL patients treated from 2001 to 2019 at 8 centres of the Polish Paediatric Solid Tumours Study Group (PPSTSG). Group characteristics at diagnosis, treatment and patterns of relapse were analysed. Observation was completed in December 2020. We analysed 286 high risk patients, including 16 infants. Isolated CNS relapse, defined as the presence of a tumour in brain parenchyma or leptomeningeal involvement, was found in 13 patients (4.5%; 8.4% of all relapses), all of whom were stage 4 at diagnosis. Isolated CNS relapses seem to be more common in young patients with stage 4 MYCN amplified NBL, and in this group they may occur early during first line therapy. The only or the first symptom may be bleeding into the CNS, especially in younger children, even without a clear relapse picture on imaging, or the relapse may be clinically asymptomatic and found during routine screening. Although the incidence of isolated CNS relapses is not statistically significantly higher in patients after immunotherapy, their occurrence should be carefully monitored, especially in intensively treated infants, with potential disruption of the brain-blood barrier.

Acute Lymphoblastic Leukemia in Children: Better Transplant Outcomes After Total Body Irradiation-based Conditioning.

BACKGROUND/AIM: Comparison of transplant outcomes in long-term follow-up of children after total body irradiation (TBI)- or chemotherapy-based conditioning allogeneic hematopoietic cell transplantation (allo-HCT). PATIENTS AND METHODS: Patients undergoing allo-HCT for Acute lymphoblastic leukemia (ALL) conditioned either with TBI (n=55) or chemotherapy (n=84) were compared. The following transplant outcomes were analyzed: overall survival (OS), event-free survival (EFS), relapse incidence (RI), and graft-versus-host-disease (GVHD)-free-relapse-free survival (GRFS). RESULTS: All analyzed long-term transplant outcomes were significantly better for patients conditioned with TBI at 2 years after transplant. OS at 2 years was 84% after TBI and 60.5% after chemotherapy-conditioning (p=0.005). Risk factor analysis showed that two factors, TBI-based conditioning and transplant in first remission of ALL, significantly improved OS, EFS, GRFS, and decreased RI. CONCLUSION: TBI-based conditioning before allogeneic HCT in children with acute lymphoblastic leukemia provides significantly better transplant outcomes, when compared to chemotherapy-based conditioning.

Unfavorable Outcome of Neuroblastoma in Patients With 2p Gain.

Background: Amplification of the MYCN oncogene is the most unfavorable genetic factor in neuroblastoma patients. However, knowledge about the clinical impact of low-level multiplication of MYCN is still insufficient. Therefore, we aimed to investigate the disease course in patients with different copy number status of MYCN. Materials and Methods: We examined 105 children diagnosed with neuroblastoma from 2010 to 2018 in five pediatric oncology centers in Poland. We determined the MYCN status at diagnosis by the interphase FISH examination and assessed the clinical outcome in patients. Results: A total of 35% of tumors presented with chromosome 2 numerical changes, 20% had MYCN amplification and 16% revealed 2p gain. Unexpectedly, we observed very low overall survival and event free survival (EFS) rates in neuroblastomas with 2p gain, which were comparable with patients with MYCN amplification. Conclusions: The 2p gain alteration should be reported as a strong unfavorable prognostic marker in neuroblastoma patients.

Outcome of Pediatric Acute Lymphoblastic Leukemia: Sixty Years of Progress.

BACKGROUND: A retrospective analysis was performed to investigate the survival outcomes in pediatric acute lymphoblastic leukemia (ALL) based on time period. We hypothesized that improvement has been obtained with the time-dependent therapeutic era and rise in the gross domestic product (GDP) and Human Development Index (HDI). MATERIALS AND METHODS: Data from 710 children who were treated for ALL between 1958 and 2018 at a single pediatric center were analyzed for probability of 5-year overall survival (pOS), event-free survival (pEFS) and relapse risk (pRR). Time periods were defined by the treatment protocols used in seven consecutive therapeutic eras. RESULTS: Over the 60-year period analyzed, pOS increased from 1.2% to 90.7%, pEFS from 1.2% to 86.6%, and pRR decreased from 98.8% to 9.9% for patients treated in the past decade. Risk of mortality for patients who received chemotherapy and hematopoietic cell transplant was reduced to 9.9% in the recent era, however, no statistically significant survival difference was found between patients treated with stem cell transplant and those not. CONCLUSION: The therapeutic era, related to improved GDP and HDI, was a statistically significant predictor of increased OS from ALL.

Impact of CMV and EBV on Immune Recovery After Allogeneic Hematopoietic Cell Transplantation in Children.

BACKGROUND/AIM: Immune recovery is a key factor in the management of patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT). This study analyzed the factors contributing to immune reconstitution after allo-HSCT. PATIENTS AND METHODS: Overall, 65 children with malignant or non-malignant diseases were included in multivariate analyses. RESULTS: The following factors contributed to a faster immune recovery: peripheral blood as a stem cell source and reactivation of CMV infection for CD3+ and CD4+ lymphocyte subpopulations; reactivation of CMV infection for CD8+ subset; donor EBV-IgG+ and no EBV reactivation for CD19 lymphocytes; recipient age below 10 years and peripheral blood as a stem cell source for NK cells. For CD2 and CD4/CD8 ratio no factor was significant in multivariate analysis. CONCLUSION: Patients receiving a graft from an EBV-IgG-positive donor and not having early EBV post-transplant viremia show faster recovery of the B-cells, while patients with early CMV-DNA-emia have a better re-establishment of T-cell subsets.

Solid Cancers in the Premature and the Newborn: Report of Three National Referral Centers.

BACKGROUND: Advances in multidisciplinary care for pediatric cancer have resulted in significant improvement in cure rates over the last decades; however, these advances have not been uniform across all age groups. Cancer is an important cause of perinatal mortality, yet the full spectrum of malignant neoplasms in newborns is not well defined. METHODS: The authors have reviewed the clinical features and outcomes of 37 newborns with congenital malignant tumors treated at three referral centers in North, Central, and South Poland between 1980 and 2014. Event-free survival (EFS) and overall survival (OS) rates were estimated by Kaplan-Meier methods and compared using long-rank test and Cox models. RESULTS: Twenty-two patients were diagnosed prenatally. The most common diagnoses were neuroblastoma (48.7%), followed by malignant germ-cell tumor (16.2%), and Wilms' tumor (8.1%). Neuroblastoma was the most common malignancy among full-term infants, and malignant sacrococcygeal teratoma was the most common malignancy in premature infants. Thirty patients (81%) are alive with a median follow-up of 4.8 years from diagnosis. Patients with Wilms' tumor and malignant germ-cell tumors had the best outcomes (5-year OS 100% for both), whereas the worst prognosis was observed for sarcoma patients (5-year OS 72.92%). Premature infants had better outcome than full-term infants (5-year OS 92.8% vs. 72.58%, respectively). CONCLUSION: Although rare, neonatal cancers can present with an aggressive clinical behavior, but they have a generally good outcome. Early diagnosis and management by expert multidisciplinary teams that integrate perinatal medicine experts with pediatric and surgical oncologists are critical. Centralized care with clear referral pathways that facilitate early initiation of specialized treatment should be prioritized.

Drug-resistance Profile in Multiple-relapsed Childhood Acute Lymphoblastic Leukemia.

AIM: To analyze the drug-resistance profile at first and subsequent relapse in children with acute lymphoblastic leukemia (ALL). PATIENTS AND METHODS: A total of 154 pediatric ALL samples were tested for ex vivo chemosensitivity for up to 19 drugs. Their combined drug resistance profile (PVA score) was analyzed. RESULTS: The median relative resistance scores between patients with multiple relapse and those with first relapse considering all drugs was 2.0. The median PVA score at subsequent relapses was 8 vs. 6 at first relapse (p=0.004). Samples from multiple-relapsed ALL were more drug resistant to: prednisolone (>1.9-fold), dexamethasone (>1.5-fold), vincristine (3.1-fold), L-asparaginase (5-fold), mitoxantrone (2.4-fold), cytarabine (4.3-fold), mercaptopurine (2.2-fold), thioguanine (4.8-fold), etoposide (2.6-fold) and melphalan (2.7-fold). Lymphoblasts at multiple relapse were comparably resistant to: daunorubicin, doxorubicin, cyclophosphamide, ifosfamide, busulfan, treosulfan, fludarabine, clofarabine and bortezomib. CONCLUSION: In comparison to first relapse, subsequent relapsed childhood ALL is more ex vivo-resistant to most tested drugs.

Ovarian function in female survivors after multimodal Ewing sarcoma therapy.

BACKGROUND: With advances in cancer care, more young women with Ewing sarcoma (ES) survive after treatment. Thus, we sought to analyze the ovarian function in prepubertal, pubertal and postpubertal females and young women receiving multimodal therapy for ES, and to identify patients at risk of infertility on whom fertility preservation would be indicated. PROCEDURES: Twenty-seven female survivors of ES were included in this retrospective multiinstitutional study. Patients were classified into four groups according to the treatment received: chemotherapy (CHT) without pelvic radiation (pRT), chemotherapy and pRT, CHT and autologous hematopoietic cell stem rescue (aHSCT) without pRT, and CHT + pRT + aHSCT. The ovarian function and fertility outcomes were analyzed. RESULTS: At a median follow-up of 5.7 years from diagnosis, and at median age at follow-up of 16.3 years, 67% of the survivors had premature ovarian insufficiency, including all patients receiving pelvic RT and 87.5% of patients who underwent aHSCT, independent of chemoprotection. Thirty-seven percent of patients had a clinical syndrome of premature menopause. The relative risk (RR) of premature ovarian insufficiency of a survivor was 3.9 (p 0.03) for pRT, and 2.4 (p 0.07) for aHSCT. On multivariate analysis, radiation therapy was a significant predictor of higher risk of premature ovarian insufficiency over chemotherapy alone. CONCLUSIONS: A large proportion of women receiving multimodal therapy for ES develop premature ovarian insufficiency. Patients and guardians should be informed about the reproductive potential and strategies for preservation of ovarian function should be considered individually. Pediatr Blood Cancer 2015;62:341-345. © 2014 Wiley Periodicals, Inc.

Internal hemipelvectomy in the management of pelvic Ewing sarcoma - are outcomes better than with radiation therapy?

BACKGROUND: Pelvic Ewing sarcoma (ES) is commonly associated with a worse prognosis. Large size and location limit local control options to radiation therapy, and local recurrences are common. We evaluated the impact of hemipelvectomy and radiation on outcomes, including function. MATERIALS AND METHODS: Thirty-nine patients (median age 13.5years) with ES of the pelvis and sacral bones were treated during the period 2000-2012. Fifteen were treated with definitive radiotherapy (RT), 9 patients underwent hemipelvectomy alone, and 15 were treated with combined hemipelvectomy and RT. RESULTS: Twenty patients (51.2%) are alive with a median follow-up 3.2years from diagnosis. Median time from diagnosis to relapse was 1.3years. Three-year estimates of EFS and OS were 47% and 61%, respectively. Patients treated with surgery or surgery with RT had better outcome than patients treated with RT only (3-year OS 78% or 81% vs. 36%, respectively, p=0.00083). The outcome of patients with pelvic ES treated with hemipelvectomy was not significantly different from the outcome of all patients with Ewing sarcoma treated on the national Polish protocol. CONCLUSIONS: Internal hemipelvectomy offers good chances of cure for patients with pelvic ES, with a reasonable rate of complications and good function.

Validation of a multi-modal treatment protocol for Ewing sarcoma--a report from the polish pediatric oncology group.

BACKGROUND: Ewing sarcoma (ES) is the second most common paediatric malignant bone tumor. Advances in multi-disciplinary care have resulted in significant improvement in cure rates over the last decades. However, the generalization of those results in countries traditionally excluded from large cooperative trials has yet to be demonstrated. We report the results of modern multi-disciplinary care for patients with ES in Poland. PROCEDURES: One hundred and thirty-two patients with ES were treated using modern multi-modal therapy during the period 2000-2009. Overall survival was estimated by Kaplan-Meier methods and compared using long-rank test and Cox models. Factors predictive of outcome in our setting were analyzed to identify distinct risk groups that could help identify areas for improvement. RESULTS: The median age at the time of diagnosis was 12.3 years. With a median follow-up of 5.0 years, the 5-year event-free survival (EFS) and OS estimates for localized disease were 54.88% and 68.29%, respectively. For patients with metastatic disease, 5-year EFS and OS estimates were 36% and 42%, respectively. There was no correlation between age and stage or site. Patients with localized, non-pelvic disease had better outcome than patients with axial tumors (71% vs. 44%, respectively, P = 0.00073). Treatment failure was associated with stage, pelvic primary, poor histological response, and type of local control. CONCLUSIONS: Successful treatment of ES requires optimal systemic and local therapy. We were able to replicate the results of modern multi-modal protocols. Validation of current treatment protocols in countries with more limited cancer treatment resources is required.

Survival and prognostic factors in children with brain tumors: long-term follow-up single center study in Poland.

AIM: Analysis of risk factors for survival in long-term follow-up of children treated at a single pediatric center in Poland. PATIENTS AND METHODS: Out of 623 children diagnosed with cancer between 1995-2005, 110 were treated for brain tumors and followed-up, with a mean survival of 11.4 years. RESULTS: Overall 5-year survival in the whole cohort was 60.9±4.7%, while 10-year survival was 58.2±4.7%. No relapse, progression or death occurred after six years from initial diagnosis. Survival was 48.1±9.6% for patients with medulloblastoma and primitive neuroectodermal tumors; 83.3±6.2% for low-grade astrocytoma; 56.6±16.6% for ependymoma, while 0% at 72 months for high-grade glioma. Patients with cerebellar tumors had a survival rate 69.0±7.1% at 10 years. Multivariate analysis showed that factors predicting poor outcome were: grade III-IV tumor, incomplete surgical resection, and complications after surgical resection, while diagnosis of low-grade glioma was the only factor predicting good outcome. Progression of the disease during therapy was an additional independent adverse risk factor for survival. CONCLUSION: Long-term survival was achieved by 58% of children with brain tumors. Advanced tumor stage, incomplete surgical resection, complications of surgical treatment, and progression of the disease during treatment predicted poor outcome.

[Chemotherapy in patients with refractory Ewing sarcoma]. / Chemioterapia u dzieci i mlodziezy z opornymna leczenie miesakiem Ewinga

BACKGROUND: Patients with metastatic, progressive or recurrent Ewing sarcoma have a poor prognosis. In addition to increasing the intensity of conventional chemotherapy, the combination of irinotecan and temozolomide has been proposed as an effective salvage regimen for some pediatric malignancies. AIM: To evaluate the effect of two different salvage regimens on the final outcome of patients with refractory Ewing sarcoma. MATERIAL AND METHODS: During the period 2008-2012, twenty-two patients (age between 2.9 -19.3 years) with recurrent or refractory Ewing sarcoma were treated with the combination of vincristine, irinotecan and temozolomide (VIT regimen), and twenty patients were treated with the combination of cisplatin, doxorubicin, cyclophosphamide and teniposide (PACE regimen). All patients had standard tumour imaging and laboratory evaluation. All toxicities were documented. The WHO criteria were used to evaluate response. Statistical analysis was performed using STATA 10.0 for Windows. Results distributions were estimated using the method of Kaplan-Meier. The log-rang test was used to compare the groups. RESULTS: A total of 91 cycles of VIT and 65 cycles of PACE were administered. For VIT therapy the overall response rate was 68.1%. Median time to progression was 3.0 months. Five patients are alive with no evidence of disease with a median follow-up of 10.3 months. For PACE therapy the overall response rate was 75%. Median time to progression was 3.5 months. Four patients are alive with no symptoms of disease with a median follow-up of 17.6 months. The 2 years overall survival probability after recurrence was 29.94%; no differences were detected between therapy groups. Toxicity for PACE was significantly higher. CONCLUSIONS: The effectiveness of VIT regimen in refractory Ewing Sarcoma is comparable to conventional chemotherapy. The VIT regimen has less associated toxicities than the PACE regimen.

Vincristine, irinotecan, and temozolomide in patients with relapsed and refractory Ewing sarcoma.

BACKGROUND: Patients with metastatic, progressive or recurrent Ewing sarcoma (ES) have a dismal outcome. The combination of irinotecan and temozolomide has been proposed as an effective salvage regimen for some pediatric malignancies. Thus, we sought to evaluate this combination with vincristine for patients with relapsed and refractory ES. MATERIALS AND METHODS: Twenty-two patients with relapsed or refractory ES were treated with the combination of vincristine (1.5 mg/m(2) i.v. day 1), irinotecan (50 mg/m(2) /day i.v. days 1-5) and temozolomide (125 mg/m(2) /day p.o. days 1-5) (VIT) during the period 2008-2012. All toxicities were documented. RESULTS: A total of 91 cycles (median 4.1 cycles/patient) were administered. A complete response (CR) was achieved in five patients, partial response (PR) in seven patients, stable disease (SD) in three patients, and progression disease (PD) in seven patients, with an overall response rate of 68.1%. Median time to progression was 3.0 months (range 1.1-37.1 months). Five patients (22.7%) are alive with no evidence of disease with a median follow-up of 10.3 months (range 2.1-46.5); four of them received consolidation with high-dose chemotherapy and autologous hematopoietic stem cell transplant after responding to VIT. Outcome was better for patients with relapsed ES compared with patients who progressed to initial therapy (estimated 2 year overall survival 36.4% vs. 0%, respectively). There were no significant toxicities. CONCLUSIONS: The shorter, 5-day VIT regimen is an active and well-tolerated regimen in refractory ES. This combination deserves further investigation in the upfront management of patients with metastatic disease.

Individual tumor response testing in multiple relapsed acute myeloid leukemia in children.

AIM: The analysis of the individualized tumor response testing (ITRT) at first and subsequent relapse in children with acute myeloid leukemia (AML). PATIENTS AND METHODS: A total of 76 pediatric AML samples underwent ITRT for up to 21 drugs. RESULTS: No significant differences between ITRT at first and subsequent relapse were found, and no drug was found, for which significantly higher resistance of myeloblasts was observed at subsequent relapse, when compared to first relapse of AML. For most tested drugs, patients with relapse had higher IRTR than those with de novo AML. The median relative resistance value between patients with relapse and those with de novo diagnosis for all 21 drugs tested was 1.6. Samples of relapsed AML samples were significantly more resistant to: Idarubicin (1.8-fold), etoposide (5.9-fold), cytarabine (1.7-fold), fludarabine (3.7-fold) and busulfan (4.3-fold). CONCLUSION: ITRT in relapsed AML is higher in comparison to that at initial diagnosis, while no differences in ITRT between first and subsequent relapse of AML were found.

Individualized tumor response testing profile has a prognostic value in childhood acute leukemias: multicenter non-interventional long-term follow-up study.

A total number of 817 children with acute lymphoblastic leukemia (ALL) and 181 with acute myeloblastic leukemia (AML) were assessed for individualized tumor response testing (ITRT) profile as a prognostic factor in long-term follow-up. For each patient, ITRT, initial response to therapy and long-term outcome were assessed. In initial ALL, an impact on long-term response was shown in ITRT for 13 drugs, while in initial AML only for cytarabine. For patients with ALL, a combined five-drug ITRT profile for prednisolone, l-asparaginase, vincristine, cytarabine and daunorubicin or doxorubicin had predictive value for probability of disease-free survival (pDFS) in univariate analysis, whereas in multivariate analysis, bone marrow response by day 33 was the only prognostic factor. For patients with AML, no factor had prognostic value for pDFS in univariate analysis, while ITRT to cytarabine almost reached significance. In conclusion, ITRT can possibly be regarded as a risk factor in childhood acute leukemias.

Comparison of prognostic value of in vitro drug resistance and bone marrow residual disease on day 15 of therapy in childhood acute lymphoblastic leukemia.

AIM: The analysis of the prognostic impact of residual disease at day 15 of induction therapy, individual tumor response testing (ITRT) at diagnosis, initial factors and initial therapy response to the risk of relapse in children with precursor B-cell acute lymphoblastic leukemia (ALL). PATIENTS AND METHODS: A total of 87 children were tested at diagnosis for ITRT and for persistence of blasts in bone marrow at day 15 (BML15>0.5%) and were followed-up in long-term analysis. RESULTS: The probability of disease-free survival (pDFS) was significantly better for patients with an ITRT profile showing sensitivity to prednisolone, vincristine, daunorubicin, and L-asparaginase. Patients with BML15>0.5% had higher ITRT for prednisolone, daunorubicin, L-asparaginase, and etoposide. Three factors had predictive impact for relapse: BML15>0.5%, ITRT for prednisolone and high combined ITRT profile for prednisolone, vincristine and L-asparaginase (PVA score). CONCLUSION: Persistence of blasts in bone marrow at day 15, ITRT showing resistance to prednisolone and high PVA score were the strongest and comparable prognostic factors predicting relapse in childhood ALL.

Identification of the genes expression profile associated with the ex vivo resistance to etoposide in childhood acute leukemias.

INTRODUCTION: Drug resistance and the gene expression profiles might discriminate the therapy outcome, and indicate the subgroup of patients with poor prognosis. In this study we analyzed the gene expression profile in correlation with the profile of ex vivo resistance to etoposide in children with acute leukemias. METHODS: The ex vivo drug resistance profile was determined by the MTT cytotoxicity assay performed on leukemic blasts of 56 patients. Gene expression profiles were obtained from the results of hybridization of cRNA to Human Genome U133A 2.0 ologonucleotide arrays. The following analyses were performed: correlation analysis, hierarchical clustering, the assignment of location and function. Verification of data for four selected genes (MNDA, GH1, NUDT21, RHOG) was performed by quantitative real time polymerase chain reaction in the studied population and in an independent group of 54 leukemic patients. RESULTS: Using the permutation Spearman correlation test, a set of 233 probes/209 genes was selected. The global test confirmed the significance of the correlation of gene expression profile and resistance to etoposide (p<0.001). The NUDT21 (nudix, nucleoside diphosphate linked moiety X-type, motif 21) gene showed the strongest correlation with resistance to etoposide (FDR<0.0001%). CONCLUSIONS: Profiling of transcriptome may help in assessing the sensitivity to drugs used in chemotherapy. Resistance to etoposide is possibly associated with a change of expression of a large number of biologically important genes that influence several cellular mechanisms.