Prognostic Significance of TEL/AML1 Fusion Transcript in Childhood B-Precursor Acute Lymphoblastic Leukemia

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Abstract
A retrospective study was conducted to investigate the prognostic significance of TEL/AML1 fusion resulting from a cryptic t(12;21) in Japanese patients with childhood B-precursor acute lymphoblastic leukemia (ALL). Leukemic samples from 144 children with newly diagnosed ALL (104 with CD10-positive B-precursor ALL, 11 with CD10-negative B-precursor ALL, 5 with B-ALL, and 24 with T-ALL) were analyzed by reverse-transcription polymerase chain reaction. The frequency of patients with TEL/AML1 was 16% (23 of 144) and all patients with TEL/AML1 also had CD10-positive B-precursor ALL. TEL/AML1 was not found in any samples from the patients with T-ALL, B-ALL, or CD10-negative B-precursor ALL. Among patients with CD10-positive B-precursor ALL, age, initial white blood cell count, and immunophenotype did not differ with TEL/AML1 positivity, although the patients were predominantly male (p 24 months after diagnosis. Although the overall 5-year survival rate was better among patients with TEL/AML1 fusion transcript than among those without it (87.3 ± 8.7% versus 75.9 ± 5.8%, respectively), the 5-year disease-free survival (DFS) rates of patients with TEL/AML1 fusion transcript and those without it were similar (64.0 ± 13.5% versus 69.1 ± 6.3%, respectively). However, for 57 patients treated with the latest intensive protocol, the 4-year DFS rate was much higher for the patients with TEL/AML1 fusion transcript than for those without it (100.0% v.s. 69.6 ± 8.4%, respectively, p = 0.1472). This study confirmed that TEL/AML1 gene fusion is the most common genetic event in pediatric ALL in Japan and is restricted to CD10-positive B-precursor ALL. Moreover, it was associated with an improved survival rate among patients treated with intensive therapy. Therefore, these data suggest that the patients with TEL/AML1 may not necessarily be candidates for less aggressive treatment.