DETECTION OF MINIMAL RESIDUAL DISEASE IN PATIENTS WITH CHILDHOOD COMMON ACUTE LYMPHOBLASTIC-LEUKEMIA AFTER AUTOLOGOUS BONE-MARROW TRANSPLANTATION WITH EX-VIVO PURGING AND SYSTEMIC IL-2 INFUSION - UNSUCCESSFUL PREDICTION OF SUBSEQUENT RELAPSE

We sequentially analyzed minimal residual disease (MRD) in 7 children with common acute lymphoblastic leukemia (cALL) after autologous bone marrow transplantation (ABMT) with ex vivo purging followed by systemic interleukin-2 infusion, After ABMT, 3 of the 7 patients remained in complete remission (CR) for more than 1 year, and 4 subsequently relapsed. MRD was estimated by polymerase chain reaction amplification to detect the leukemia clone-specific immunoglobulin heavy chain third complementarity determining region (IgH CDR-III). The IgH CDR-III sequences from the relapsed patients were identical with those determined at each respective initial diagnosis. In 2 patients, the levels of MRD were 10(-2) and 10(-5) in the harvested bone marrow (BM) cells, and even after purging the levels were 10(-4) and 10(-5) cells, respectively, One of the 2 patients relapsed 3 months after ABMT, while the other remained in CR for 33 months after ABMT, Among the 4 patients who subsequently relapsed after ABMT, MRD was not detected in the BM samples even 1 month before relapse, Our results suggest that PCR-negativity does not necessarily indicate a lower risk of subsequent relapse, Detection of MRD tends to favor the assessment of the therapeutic effects rather than prediction of relapse.