The prognosis of CALM-AF10 positive adult T-cell acute lymphoblastic leukemias depends on the stage of maturation arrest.
Résumé
: CALM-AF10 (also known as PICALM-MLLT10) is the commonest fusion protein in T-cell acute lymphoblastic leukemia, but its prognostic impact remains unclear. Molecular screening at diagnosis identified CALM-AF10 in 30/431 (7%) T-cell acute lymphoblastic leukemia patients aged 16 years and over and 15/234 (6%) in those aged up to 15 years. CALM-AF10 positive patients were predominantly (72%) surface (s)CD3/T-cell receptor negative in adults, but predominantly (67%) T-cell receptor positive in children. Amongst 22 adult CALM-AF10+ patients treated according to the LALA94/GRAALL03-05 protocols, the poor prognosis for event-free survival (p=0.0017) and overall survival (p=0.0014) was restricted to the 15 T-cell receptor negative cases. Amongst CALM-AF10+ T-cell receptor negative patients, 82% demonstrated an early T-cell precursor phenotype, reported to be of poor prognosis in pediatric T-cell acute lymphoblastic leukemia. Early T-cell precursor acute lymphoblastic leukemia corresponded to 22% of adult LALA94/GRAALL03-05 T-cell acute lymphoblastic leukemias, but had no prognostic impact per se. CALM-AF10 fusion within early T-cell precursor acute lymphoblastic leukemia (21%) did, however, identify a poor prognostic group for event-free survival (p=0.04). CALM-AF10 therefore identifies a poor prognostic group within sCD3/T-cell receptor negative adult T-cell acute lymphoblastic leukemias and is over-represented within early T-cell precursor acute lymphoblastic leukemias, where it identifies those likely to fail treatment. Its prognosis and overlap with early T-cell precursor acute lymphoblastic leukemia in pediatric T-cell acute lymphoblastic leukemia merits analysis. The clinical trial GRAALL was registered at Clinical Trials.gov number NCT00327678.