randomization was stratified according to whether cns leukemia occurred at initial diagnosis of acute lymphocytic leukemia ( all ) ( stratum i , 15 patients ) , during first bone marrow ( bm ) remission ( stratum ii , 49 patients ) , simultaneous with first bm relapse ( stratum iii , 12 patients ) , or during second bm remission ( stratum iv , 11 patients ) .
C0023449
acute lymphocytic leukemia
C0005953
bm