Prognostic relevance of TLX3 (HOX11L2) expression in childhood T-cell acute lymphoblastic leukaemia treated with Berlin-Frankfurt-Munster (BFM) protocols containing early and late re-intensification elements

P>TLX3 expression (TLX3+) in childhood T-cell acute lymphoblastic leukaemia (T-ALL) seems to be associated with a poor prognosis when treated with regimens that lack early and/or late re-intensification therapy elements. Because such elements are essential components of the ALL-BFM (Berlin-Frankfurt-Munster) protocols, we evaluated whether TLX3+ T-ALL patients benefit from this type of therapy. Thirty-one/131 childhood T-ALL cases (24%) enrolled into four population-based Austrian ALL-BFM therapy studies were TLX3+. The male to female ratio was 3 center dot 5:1 and median age and leucocyte count at diagnosis were 8 center dot 7 years and 58 center dot 9 x 109/l, respectively. Twenty-four patients (77%) were good responders to prednisone. All were in complete remission after induction therapy. After a median observation time of 4 center dot 9 years (range 0 center dot 4-16 center dot 1 years) 28/31 TLX3+ cases remained in first complete remission after chemotherapy with one after additional stem cell transplantation. Although molecular disease was frequently present after a 4-drug induction therapy, final treatment outcome was excellent indicating that TLX3+ T-ALL cases may benefit from a BFM-type of ALL therapy with early and late re-intensification elements. Moreover, the fact that 2/3 relapses were also NUP214-ABL1+ suggests that these cases might represent the particular risk-prone TLX3+ subgroup that could benefit from a targeted tyrosine kinase inhibitor therapy.