PCR-POSITIVITY IN HARVESTED BONE-MARROW PREDICTS RELAPSE AFTER TRANSPLANTATION WITH AUTOLOGOUS PURGED BONE-MARROW IN CHILDREN IN 2ND REMISSION OF PRECURSOR B-CELL ACUTE-LEUKEMIA

Purging of autologous bone marrow (BM) grafts of children in second re mission after a relapse of precursor B acute lymphoblastic leukaemia ( ALL) in the BM has been carried out in our laboratory since 1987, init ially by complement mediated cell lysis. This protocol was extended by performing an immunorosette depletion before lysis with complement, T he aim of the present study was to assess by polymerase chain reaction the presence of residual leukaemic cells in the BM grafts before and after purging. The results were then correlated to clinical outcome. I n 24/28 patients a PCR product was obtained by amplification of IgH an d/or TcR junctional regions. BM before purging was available for analy sis in 13 patients. We found that leukaemic cells could be detected in 8/13 (62%) of these grafts before purging. All these eight patients e xperienced a relapse, regardless of whether the purging procedure had been successful (defined as achievement of FOR-negativity) or not. In contrast, none of the five patients with PCR-negative grafts before pu rging relapsed (P = 0.0072). One patient died due to transplant-relate d toxicity. Of the remaining 23 patients, nine patients received a PCR -positive BM graft after purging. All these nine patients experienced a relapse as compared to 6/14 whose BM was PCR-negative after purging (P = 0.0072). Two of eight PCR-positive BM grafts could be purged to P CR-negativity. Thus, improvements both in treatment of leukaemia and i n purging efficacy are still needed.