Purpose: In adult T-lymphoblastic leukemia (T-ALL) disease-free survival remains limited to 32% to 46%. The adverse prognosis in T-ALL has not been attributed to cytogenetic or molecular aberrations. We have determined the prognostic impact of the oncogenic transcription factor ERG in T-ALL.
Patients and methods: ERG expression was analyzed by real-time polymerase chain reaction (PCR) in 105 adults with newly diagnosed T-ALL treated on the German ALL protocols. Patients were dichotomized at ERG's median expression into low (n = 52) and high (n = 53) expressers. Homeobox (HOX) 11 and HOX11L2 expression was determined by real-time PCR.
Results: High ERG expressers compared with low ERG expressers had an inferior overall survival (OS, P = .02; 5-year OS: high ERG 26% v low ERG 58%) and relapse-free survival (RFS, P = .003; 5-year RFS: high ERG 34% v low ERG 72%). On multivariable analysis high ERG expression (P = .005), immunophenotypic subgroups (early v mature v thymic T-ALL; overall P = .04), HOX11L2 positivity (P = .055), and absence of HOX11 (P = .017) were independent adverse risk factors predicting RFS. Patients with high ERG expression had a hazard ratio (HR) for relapse of 3.2. Within the good prognostic subgroup of thymic T-ALL (n = 57), high ERG (HR, 4.1; P = .02) and presence of HOX11L2 (HR, 6.6; P = .008) were independent adverse factors for RFS.
Conclusion: High expression of ERG is an adverse risk factor in adult T-ALL. Within thymic T-ALL, otherwise classified as standard-risk, high ERG expression-identified patients that were four times more likely to fail long-term RFS. The prognostic impact of ERG may assist treatment stratification and suggest the need of alternative regimens.