flowcytometric and dna analysis minimal residual disease (mrd) in childhood b-lineage lymphoblastic leukemia

background: induction chemotherapy for acute lymphoblastic leukemia achieves complete remis sion in over 90% of children. it is apparent therefore that many patients in clinical remission and with out residual disease detectable by conventional light microscopy of peripheral blood or bone marrow films still harbor viable cells of the original disease mrd analysis does have a useful role to play in the risk directed treatment of childhood all and this is currently being investigated in large prospective studies. methods: we have investigated mrd in bone marrow samples by three color flowcytometry approach in 63 pediatric b-precursor all patients treated according to bfm all 95 protocol. bone marrow samples were collected from children at three different times including: day 28th, at the beginning of intensified therapy and at the end of therapy .cells with leukemia associated immunophenotype were investigated by dna analysis for evaluation of dna content. results: among 63 children with diagnosis of b-lineage all and quantified for post induction residual disease study .we observed that the mean number of blast cells have significant differences among these groups. the mean number of leukemic blasts counted on day 28 was 2.7± 0.4, at the beginning of intensified therapy 1.7±0.4, and at the end of treatment 0.5±.2. these patients were in complete re mission in light microscopy examination. relapse of all was demonstrated in six of 63 children (9.5%) whose mrd were more than one blast in 10-2 cells .comparing this to light microscopic exami nation dill of  these patients had 4-5% blasts vs. 1% for those who did not relapse. conclusion: mrd analysis does have a useful role in the risk directed treatment of child hood all and the investigation of levels and the dynamics of mrd by sensitive and quantitative flowcytometry and pcr methods reduce false negative results. however a good morphology is also valuable.