Introduction: The CYP450 complex participates in the metabolism of ifosfamide, an antineoplastic drug used to treat solid tumors. genes contain several single nucleotide polymorphisms (SNPs) that confer different activity towards the enzyme. The aim of our study was to analyze gene frequencies of allelic variants and their association with ifosfamide blood levels and patient prognosis. Material and methods: 148 DNA samples from children were analyzed. Genotyping was performed by real-time PCR with TaqMan probes and ifosfamide levels were determined in dried blood drop by UPLCMS/MS. Results: Ifosfamide levels increased according to the genotype, and patients with the variant rs1799853 in CYP2C9 genotype CC had lower levels of ifosfamide (median = 1.8 μmol/l, Q 25 0.9-Q 75 4.6) compared with patients with genotype TT + CT (median = 2.8 μmol/l, Q 25 1.9-Q 75 5.1), p < 0.001. In the case of the rs2740574 variant in the CYP3A4 gene, patients with normal genotype (TT) presented median = 1.4 μmol/l, (Q 25 0.7-Q 75 2.7), while patients with the CC + TC genotype had higher levels of ifosfamide (median = 2.0 μmol/l, Q 25 1.0-Q 75 4.3), p = 0.024. In addition, patients with CC + CT genotype of this variant had a higher risk of non-response to treatment compared to patients with TT genotype (RR = 1.3, 95% CI: 1.07-1.59, p = 0.03). Conclusions: Polymorphisms in CYP2C9 and CYP3A4 genes are associated with high levels of ifosfamide. In addition, the polymorphism rs2740574 in CYP3A4 was associated with a worse therapeutic response.

BackgroundIn childhood cancer, consolidation treatment with chemotherapy followed by autologous hematopoietic progenitor stem cell transplantation is currently an accepted treatment modality in patients with high-risk solid tumors or in patients who have relapsed after conventional treatment. ObjectivesThe objective of this study was to describe the results of transplantation of a group of children who had high-risk solid tumors or relapsed after conventional chemotherapy regimens. MethodsA retrospective analysis was conducted from January 1998 to October 2004 of all children with pathologic diagnoses of high-risk solid tumors or children that had previously relapsed after conventional chemotherapy and that were subsequently submitted to autologous hematopoietic progenitor stem cell transplantation. The analysis included overall survival rates, event-free survival rates, mortality rates and chemotherapy complications. ResultsNineteen patients were submitted to this approach. The age range was from 27 to 196 months with a median age of 52 months. The overall survival rate at 100 days was observed in 79%, the three-year event-free survival rate was 63%. The mortality rate secondary to the myeloablative chemotherapy regimen was 21% (n = 4). Only three patients (15.8%) relapsed with tumor progression after transplant. ConclusionAutologous hematopoietic progenitor stem cell transplantation is still a successful procedure in patients with solid tumors refractory to conventional chemotherapy.