Minimal residual disease in the bone marrrow of children with isolated extramedullary relapse of ALL

The extent of bone marrow (BM) involvement at diagnosis of childhood isolated extramedullary relapse (IEMR) of acute lymphoblastic leukemia (ALL) and its reduction during induction therapy at minimal residual disease (MRD) level has never been systematically analysed and related to prognosis. We have quantified the extent of sub-cytological BM involvement at relapse diagnosis in 22 patients with first relapse in the central-nervous-system or in the testis treated according to the ALL-REZ BFM protocols (90/96/02). MRD has been sensitively assessed by real-time-quantitative PCR using T-cell-receptor and Immunoglob…