Thiopurine methyltransferase polymorphisms in children with acute lymphoblastic leukemia.

INTRODUCTION: Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. 6-mercaptopurine (6-MP) and methotrexate are backbone drugs for maintenance phase of treatment. Purine Analogs 6-MP/6-thioguanine/azathiopurine are metabolized to its inactive form by the enzyme thiopurine methyltransferase (TPMT). Ninety percent of the population harbor wild type on both alleles (TPMT wild/wild), 10% are heterozygous, that is, one allele is mutant (TPMT wild/mutant) and 0.3% are homozygous, that is, both allele are mutant (TPMT mutant/mutant). In heterozygous and homozygous variant, activity of enzyme is low, leading to a higher incidence of toxicity (myelosuppression). AIM: The primary objective was to access the polymorphism of the enzyme, TPMT, in Children with ALL. Secondary objective was to correlate TPMT genotype with 6-MP toxicities. MATERIALS AND METHODS: Seventy-two children with newly diagnosed ALL during first maintenance phase were serially enrolled after obtaining consent. Five ml of peripheral blood was drawn and DNA extracted. TPMT 2 polymorphisms were performed using Allele specific polymerase chain reaction (PCR) and TPMT 3B and 3C are performed by PCR-restriction fragment length polymorphism. RESULTS: Sixty-nine children of 72 (95.8%) were wild for TPMT polymorphism and 3 (4.2%) were heterozygous for TPMT. Among the heterozygous variant one each (33.3%) were heterozygous for 2A, 3A, 3C. Febrile neutropenia was the most common toxicity in both wild and heterozygous group. CONCLUSION: The frequency of TPMT polymorphisms in children with ALL is 4.2%. Heterozygous variant is this study are one each (33%) of 2A, 3A, 3C.

Response to imatinib mesylate in childhood chronic myeloid leukemia in chronic phase.

INTRODUCTION: Childhood chronic myeloid leukemia (CML) accounts for less than 3% of all childhood leukemias, hence, data on imatinib (IM) in adult CML patients has been largely extrapolated to children. We have analyzed our data to add to the existing literature. AIMS: Primary objective is to assess the progression-free survival (PFS). Secondary objective are cytogenetic response, overall survival (OS), and toxicities. SETTINGS AND DESIGN: This is a retrospective analysis from the case records from a single institution. MATERIALS AND METHODS: Institutional ethics committee approval was obtained. All the children diagnosed CML in chronic phase (CML-CP) aged less than 18 years registered between 2000 and 2009 were enrolled. All the patients were started on IM at 260 mg/m(2). STATISTICAL ANALYSIS: Kaplan-Meier curves were used to calculate the PFS and OS. RESULTS: There were 64 children with median age of 13 years (range, 1-18) with male predominance (male:female (M: F) - 1.85:1). Sixty-one patients (95.4%) achieved complete hematological response (CHR) at median of 8 weeks. Thirty-seven (57.8%) patients had evaluation of cytogenetic response and were subjects for outcome analysis. The median time to best cytogenetic response evaluation was 13 months (range, 4-52). Twenty-nine patients (78.3%) achieved complete cytogenetic response (CCyR). At a median follow-up of 36 months (range 5-75), 21 (56.8%) remained progression free and 35 (94.5%) are alive. Adverse events were tolerable. CONCLUSIONS: PFS at a median follow-up of 36 months is 56.8% and OS 94.5%.