Therapy of advanced-stage mature B-cell lymphoma and leukemia in children and adolescents with rituximab and reduced intensity induction chemotherapy (B-NHL 2004M protocol): the results of a multicenter study.

Pediatric mature B-cell non-Hodgkin lymphomas (B-NHLs) are highly aggressive malignant tumors that are curable with chemotherapy (ChT). High-dose methotrexate (MTX) is considered indispensable for successful treatment, but this therapy frequently induces severe mucositis and infectious complications, especially in induction, which can cause treatment failure. A prospective multicenter trial of combined immunochemotherapy for advanced-stage B-NHL with rituximab and the modified NHL-BFM-90 protocol was conducted. The major differences from the original protocol were a decrease in the dose of MTX from 5000 to 1000 mg/m/24 h in the first 2 ChT blocks and the addition of rituximab at 375 mg/m to each of the first 4 blocks of ChT. Eighty-three newly diagnosed patients with a median age of 8.84 years with Burkitt lymphoma/leukemia and diffuse large B-cell lymphomas stage III to IV were included. Four patients died during induction ChT due to tumor lysis syndrome and infection. Two additional patients died subsequently due to tumor resistance. Complete remission was achieved in 77 (92.8%) patients; 2 patients relapsed at 1 and 3 months, and 2 developed secondary malignancies at 1 and 6.5 years, respectively, after the completion of therapy. The overall survival probability was 82%±8% with a median follow-up of 65.2 months. Combined therapy with rituximab and intensive ChT with a reduced MTX dose of 1 g/m in the 2 induction courses was feasible and produced high cure rates in patients with pediatric advanced-stage mature B-NHL.

TPMT genetic variations in populations of the Russian Federation.

BACKGROUND: Polymorphisms that reduce the activity of thiopurine S-methyltransferase (TPMT) cause adverse reactions to conventional doses of thiopurines, routinely used for antileukemic and immunosuppressive treatment. There are more than 20 variant alleles of TPMT that cause decreased enzymatic activity. We studied the most common variant alleles of TPMT and their frequency distribution in a large cohort of multiracial residents in the Russian Federation and compared their frequencies in children with and without malignancy to determine whether TPMT gene abnormality is associated with hematologic malignancy. PROCEDURE: The TPMT biochip was used to detect 6 TPMT single nucleotide polymorphisms (SNPs) corresponding to 7 TPMT-deficiency alleles (TPMT*2, TPMT*3A, TPMT*3B, TPMT*3C, TPMT*3D, TPMT*7, and TPMT*8). We analyzed allele frequencies in the whole cohort, the childhood cancer group, and the non-cancer group. We also characterized disease features and outcome according to the presence of TPMT SNPs in children with acute lymphoblastic leukemia (ALL). RESULTS: Fifty-five (5.5%) study participants overall had heterozygous TPMT genotypes (1 variant and 1 wild-type allele): TPMT*1/*3A (n = 45; 4.5%), TPMT*1/*3C (n = 8; 0.8%), and TPMT*1/*2 (n = 2; 0.2%). TPMT SNPs were more frequent in children with hematologic malignancy than in other participants (7.5% vs. 4.0%, P = 0.02). We found no significant association between TPMT SNPs and ALL treatment outcome (median follow-up, 31.3 months). CONCLUSIONS: TPMT*3A is the most prevalent variant allele in the Russian Federation. The estimated frequency of variant alleles in the study cohort (5.5%) was similar to that observed in the White populations in the U.S. and Eastern Europe.

Rapid genotyping of common deficient thiopurine S-methyltransferase alleles using the DNA-microchip technique.

Thiopurine drugs are metabolized, in part, by S-methylation catalyzed by thiopurine S-methyltransferase (TPMT). Patients with very low or undetectable TPMT activity are at high risk of severe, potentially fatal hematopoietic toxicity when they are treated with standard doses of thiopurines. As human TPMT activity is controlled by a common genetic polymorphism, it is an excellent candidate for the clinical application of pharmacogenetics. Here, we report a new molecular approach developed to detect point mutations in the TPMT gene that cause the loss of TPMT activity. A fluorescently labeled amplified DNA is hybridized with oligonucleotide DNA probes immobilized in gel pads on a biochip. The specially designed TPMT biochip can recognize six point mutations in the TPMT gene and seven corresponding alleles associated with TPMT deficiency: TPMT*2; TPMT*3A, TPMT*3B, TPMT*3C, TPMT*3D, TPMT*7, and TPMT*8. The effectiveness of the protocol was tested by genotyping 58 samples of known genotype. The results showed 100% concordance between the biochip-based approach and the established PCR protocol. The genotyping procedure is fast, reliable and can be used for rapid screening of inactivating mutations in the TPMT gene. The study also provides the first data on the frequency of common TPMT variant alleles in the Russian population, based on a biochip analysis of 700 samples. TPMT gene mutations were identified in 44 subjects; genotype *1/*3A was most frequent.