Detection of CALM-AF10 Fusion Transcript Does Not Predict A Poor Prognosis in Children with T-Lineage Acute Lymphoblastic Leukemia Treated with AIEOP ALL 2000 Protocol and Subsequent Modified 2000 Study (R-2006).

T-ALL accounts for about 15% of pediatric ALL and still represents a clinical challenge, because more than 20% of children experience a recurrent disease which has a dismal prognosis. Characterization of molecular alterations with prognostic impact may be useful for an early identification of patients at high risk of failure in whom more intensive treatments, including hematopoietic stem cell transplantation (HSCT) may be considered. CALM-AF10 results from a recurring t(10;11)(p13;q14-21) chromosomal translocation and is the most frequent fusion transcript in both adult and pediatric patients with T-ALL. Its presence has been associated with a poor prognosis (Asnafi V et al. Blood 2003; van Grotel M et al Haematologica 2006). The aim of the present study was i) to define the incidence of CALM-AF10 among homogeneously treated children with T-ALL and ii) to evaluate the outcome of these patients.

We studied 201 patients with T-ALL, diagnosed and enrolled between 9/2000 and 12/2007 in the ALL-2000 protocol and the subsequent modified 2000 study (ALL-R-2006) of the Associazione Italiana di Ematologia ed Oncologia Pediatrica (AIEOP) which consist of an intensive chemotherapy strategy based on BFM-ALL schedules. Patients were mainly stratified according to prednisone response evaluation (good response: blast count at day 8 less than 1000/mmc) and detection of minimal residual disease (MRD) performed at day 33 (Timepoint 1) and at day 78 (Timepoint 2). When both TPs were negative children were considered to be at Standard Risk (SR); patients with TP1 and/or TP2 positive and TP2 '10^-3 were considered to be at Intermediate Risk (MR); children with TP2 positive ≥10^-3 belong to the high risk (HR) group. Patients with prednisone poor response and MRD-HR were considered eligible for HSCT from a sibling donor in first complete remission. Event free survival (EFS) and overall survival (OS) estimates with 95% CIs were calculated through the Kaplan-Meier method and differences compared with the log-rank test. RT-PCR reactions for detection of CALM-AF10 were performed as previously reported (Asnafi V et al Blood 2003)

Ten patients resulted not eligible and were excluded from analysis. Among the 191 evaluable children with T-ALL, 14 (7,3%) were positive for CALM-AF10. Twelve (85%) of these patients were males. Median age was 8 years (range 2 – 13). Immunophenotyping showed thymic/intermediate features in 6 cases, mature in 5, early in 1, biclonal in 1 and unknown in 1, respectively. Eight cases showed a poor prednisone (PDN) response. Based on a randomized study performed in induction in the frame of the ALL-2000 protocol on the efficacy of PDN vs dexametasone (DXM) 8 children were treated with PDN and 3 with DXM The remaining 3 cases, belonging to the ALL R-2006 protocol, were treated with DXM (n=2) and PDN (n=1). MRD-based stratification allowed the allocation of 3, 8 and 3 patients in the SR, MR and HR, respectively. Four cases relapsed (3 in the central nervous system and 1 in the bone marrow). EFS at 5 years of the 14 CALM-AF10 positive T-ALL children versus the 177 who were negative was 70.1% vs 63.9%, respectively (p-value log-rank=0.61). Small numbers did not allow to fully evaluate the impact of different variables such as initial steroid treatment (PDN vs DXM) or the MRD-based risk-group assignment

This study performed in a vast cohort of children with T-ALL shows that CALM-AF10 is found in about 7% of children with T-ALL and that does not predict a poor outcome when an intensive chemotherapy strategy is employed.

No relevant conflicts of interest to declare.