Childhood secondary ALL after ALL treatment.

Data on secondary acute lymphoblastic leukaemia (sALL) following ALL treatment are very rare. However, the incidence might be underestimated as sALLs without a significant lineage shift might automatically be diagnosed as relapses. Examination of immunoglobulin and T-cell receptor gene rearrangements brought a new tool that can help in discrimination between relapse and sALL. We focused on the recurrences of childhood ALL to discover the real frequency of the sALL after ALL treatment. We compared clonal markers in matched presentation and recurrence samples of 366 patients treated according to the Berlin-Frankfurt-Munster (BFM)-based protocols. We found two cases of sALL and another three, where the recurrence is suspicious of being sALL rather than relapse. Our proposal for the 'secondary ALL after ALL' diagnostic criteria is as follows: (A) No clonal relationship between diagnosis and recurrence; (B) significant immunophenotypic shift--significant cytogenetic shift--gain/loss of a fusion gene. For the sALL (A) plus at least one (B) criterion should be fulfilled. With these criteria, the estimated frequency of the sALL after ALL is according to our data 0.5-1.5% of ALL recurrences on BFM-based protocols. Finally, we propose a treatment strategy for the patients with secondary disease.

Efficacy of high-resolution comparative genomic hybridization (HR-CGH) in detection of chromosomal abnormalities in children with acute leukaemia.

The efficient detection of chromosomal aberrations in childhood acute leukaemias presents a significant component in the diagnostics of this frequent malignant disease. We used comparative genomic hybridization (CGH) and high-resolution comparative genomic hybridization (HR-CGH) to determine the frequency of chromosomal changes in 33 children with acute leukaemia (AL). The yields of chromosomal abnormalities were compared with the results obtained using conventional cytogenetics (G-banding) and fluorescence in situ hybridization (FISH). Conventional cytogenetics revealed chromosomal changes in 17 (52 %) of studied patients. The employment of FISH together with G-banding analysis identified chromosomal changes in 27 (82 %) of the AL patients investigated. CGH detected changes in DNA copy numbers in 24 (73 %) patients, 40 losses and 67 gains were found in total. HR-CGH disclosed 98 losses and 97 gains in 26 (79 %) patients. In comparison with CGH, HR-CGH analyses unveiled 88 new chromosomal aberrations: 58 losses and 30 gains. The most commonly gained chromosomes were 21 (22.5 %), X (15 %), 18 (12,5 %) and 17 (10 %). The most common losses involved sub-regions or arms of chromosomes 7 (15 %), 9 (12.5 %), 16, 19 and 1 (10 % each). Cytogenetic and molecular cytogenetic analyses of 33 childhood acute leukaemias revealed chromosomal changes in total 31 (94 %) patients. The evaluation of HR-CGH sensitivity proved that the minimal cell population of malignant cells in which a certain chromosomal change could be found was close to the 20 - 30 % level. Our results confirm the benefits of HR-CGH in detecting chromosomal changes in childhood AL. Supplementing G-banding and FISH with the HR-CGH diagnostic method increases the detection of unbalanced structural chromosomal rearrangements and can reveal small cell clones with gains and losses of whole chromosomes in hyperdiploid AL.

High-dose methotrexate and/or leucovorin rescue for the treatment of children with lymphoblastic malignancies: do we really know why, when and how?

Methotrexate (MTX) remains a mainstay in the treatment of children with hematological malignancies. The availability of an antidote/rescue agent, leucovorin (LV) has allowed escalation of MTX doses to achieve enormous plasma concentrations, compared with plasma folate. However, a recent review of more than 40 trials for children with ALL concluded that the addition of high dose MTX (HDMTX) in many different doses and schedules did not improve CNS therapy and made only minor improvements in systemic therapy for children with ALL [11]. Some assessment suggested that by HDMTX benefits only limited amount of children with ALL. Recent treatment schedules vary markedly in terms of timing, dosing and scheduling of MTX and/or leukovorin, which may leave us uncertain with ideas such as "how should we best use HDMTX and LV?" or "why are we still using such by industry recommended doses of MTX?" The answer of how best to incorporate HDMTX and/or LV into ALL treatment plans is still not known and further clinical and pharmacological studies dealing with still controversial systemic MTX issue are actual even now, after more than 5 decades of clinical experiences with the MTX in pediatric oncology.