Peripheral blast counts at diagnosis of late isolated bone marrow relapse of childhood acute lymphoblastic leukemia predict response to salvage chemotherapy and outcome. Berlin-Frankfurt-Münster Relapse Study Group.

PURPOSEIn newly diagnosed childhood acute lymphoblastic leukemia (ALL), a high tumor burden indicates a poor prognosis, while no such link has been established yet after relapse. The impact of the absolute peripheral blast count (PBC) at the time of relapse on the response to salvage chemotherapy after a late isolated bone marrow (BM) relapse is the subject of this prospective analysis.PATIENTS AND METHODSSince 1983, 260 children with a first isolated BM relapse of ALL that occurred 6 months or later after elective cessation of front-line therapy were enrolled onto four consecutive multicenter trials of the Berlin-Frankfurt-Munster (BFM) Relapse Study Group. All patients received intensive multiagent induction and consolidation chemotherapy for 6 months, followed by maintenance therapy with methotrexate (MTX) and thioguanine for 2 years. Treatment of subclinical meningeal leukemia consisted of high-dose intravenous MTX and intrathecally administered cytostatic drugs, which was augmented by cranial irradia...