Clinical outcome of patients with childhood acute lymphoblastic leukaemia and an initial leukaemic blood blast count of less than 1000 per microliter

Background: One of the strongest predictive factors for therapy outcome in childhood acute lymphoblastic leukaemia (ALL), treated according to ALL-BFM protocols, is the response to initial prednisone treatment. Prednisone res ponse is characterized by the peripheral leukaemic blast count. The thresho ld value for the characterisation as good or poor prednisone response is 10 00 blasts/mul on day eight of initial prednisone treatment. It is frequentl y being discussed, whether patients with ALL that initially present with < 1000 blasts/mul and still show < 1000 blasts/mul by day eight of treatment, have the same therapy outcome as prednisone good-responders with initially greater than or equal to 1000 blasts/mul. Patients and methods: We evaluat ed all patients included in the ALL-BFM 90 study showing good prednisone re sponse. This group included 660 patients presenting with < 1000 blasts/mul at diagnosis. We compared these patients with the prednisone good-responder s that initially presented with greater than or equal to 1000 blasts/mul. I n addition we analysed all patients who showed an increasing blast count wi thin the threshold of 1000 blasts/mul by day eight of treatment. Results: C hildren presenting with ALL and < 1000 blasts/mul at diagnosis showed a sma ll but significantly better outcome than prednisone good-responders with in itially greater than or equal to 1000 blasts/mul (5 year pEFS 0.86 vs. 0.81 , P value 0.0064). If analyzed by treatment group, no significant differenc es were found. Patients with < 1000 blasts/mul on day eight of treatment bu t increasing blast count from diagnosis until day eight did not perform wor se. Conclusion: The prognostic value of the prednisone response is not rest ricted to childhood ALL patients presenting with < 1000 blasts/mul at diagn osis, but retains its strength as a strong predictor of treatment outcome a lso in patients with < 1000 blasts/mul at diagnosis.