The Importance of Pharmacogenomic Variations in the Treatment of Children with Acute Lymphoblastic Leukemia

• Published in: Blood 2008-11, Vol.112 (11), p.4847-4847
• Main Authors: Hu, Chung-Yi, Chang, Sheng-Kai, Yang, Yung-Li, Lin, Shu-Wha, Chiu, Rong-Jing, Lin, Kai-Hsin, Jou, Shiann-Tarng, Lu, Meng- Yao, Chang, Hsiu-Hao, Lin, Kuo-Sin, Lin, Dong-Tsamn
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V112.11.4847.4847

In adaptation of risk-directed combined chemotherapies, the initial remission rate in treatment of childhood acute lymphoblastic leukemia (ALL) has exceeded 95%. Hematological relapse during maintenance therapy, in which methotrexate (MTX) and thiopurine are applied, is the major cause of treatment failure. A retrospective study was performed to evaluate the role of pharmacogenomic effects in the treatment of children with ALL in the southern Chinese population. A total of 105 Taiwanese children with ALL, who received combined chemotherapy of different intensities based on risk-directed Taiwan Pediatric Oncology Group (TPOG)-ALL-93 protocols between Oct. 1993 to Dec. 2001, were recorded in long-term follow-up (6.5 to 13.7 years) for events (hematological relapse or death) occurrence (Figure 1). Seventeen genetic polymorphisms in 13 pharmacogenomic targets that implicated in MTX/thiopurine metabolism were analyzed by PCR-based restriction length polymorphism (RFLP) or sequence-specific oligonucleotide (SSO) probe hybridization. Pharmacogenomic polymorphisms were correlated with long-term event-free survival (EFS) of patients, with confounding effects adjusted by multivariate regression. Homozygosity of the 2677–3435 G-C allele in the multi-drug resistance gene (MDR-1, ABCB1) was highly associated with a significant reduction in long-term EFS in those patients treated with the standard risk protocol (TPOG-ALL-93-SR) (Figure 2). In the 36 patients receiving TPOG-ALL-93-SR treatment protocol, 6 out of 12 (50%) subjects carried homozygotic MDR1 2677–3435 G-C/G-C genotype suffered hematological relapse in 2 years, compared to 21 of 24 (88%) the non-homozygotic subjects remained event-free after 5 years (hazard ratio: 6.8, p=0.01). Among patients treated with the a high risk protocol (TPOG-ALL-93-HR) due to the presence of myeloid markers on the leukemic cells or manifested central nervous system leukemia, the thymidylate synthase (TYMS) enhancer 28-bp repeats 3R3R, and the glutathione-S-transferase M1 (GSTM1) null genotypes were associated with inferior clinical outcomes (p=0.029 and 0.058, respectively). Moreover, for patients with T-cell ALL that received the very high risk protocol (TPOG-ALL-97-VHR), the methionine synthase reductase (MTRR) 66AA genotype correlated with a superior prognosis compared to the AG or GG genotypes. These findings indicated independent pharmacogenomic determinants could be identified in subsets of Taiwanese children with ALL and cor