Background: The absence of biallelic TCRγ deletion (ABD) is a characteristic of early thymocyte precursors before V(D)J recombination. The ABD was reported to predict early treatment failure in T-cell acute lymphoblastic leukemia (ALL). This study aimed to investigate its prognostic value in Taiwanese patients with T-cell ALL. Procedure: Forty-five children with T-cell ALL were enrolled from six medical centers in Taiwan. Quantitative DNA polymerase chain reaction (Q-PCR) was performed to check the status of TCRγ deletion. The threshold for homozygous deletions by Q-PCR was defined as a fold-change <0.35. Results: ABD was found in 20 patients [20:45] who had higher incidences of induction failure than those without ABD (P=0.03; hazard ratio [HR]=8.13; 95% confidence interval [95% CI]=1.23-53.77) after multivariate regression analysis. Patents with ABD also had inferior EFS and OS (P=0.071 and 0.0196, respectively). Multivariate Cox analysis indicated that the association between ABD and overall survival was independent of age and leukocyte count on presentation (P=0.036; HR=4.25; 95% CI=1.10-16.42). Conclusions: The absence of TCRγ deletion is a predictor of a poor response to induction chemotherapy for pediatric patients with T-cell ALL in Taiwan. Providing patients with T-cell ALL and ABD with alternative regimens may be worthwhile to test in future clinical trials.
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