New treatment strategies in childhood acute lymphoblastic leukaemia

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6-mercaptopurine, a key drug for the treatment of acute lymphoblastic leukaemia in children, is a prodrug metabolized into 6-thioguanine (6-TGN) which are the active compounds and into methylated metabolites, primary by thiopurine S-methyltransferase enzyme (TPMT). This enzyme displays important inter subject variability linked to a genetic polymorphism: when treated with standard doses of thiopurine, TPMT-deficient and heterozygous patients are at great risk for developing severe and potentially life-threatening toxicity (hematopoietic, hepatic, mucositis. . . ) but show a better survival rate while patients with high TPMT activity (wild type) present lower peripheral red blood cells 6-TGN concentrations and a higher risk of leukemia relapse. Genotyping remains crucial before 6-MP administration at diagnosis to identify patients with homozygous mutant TPMT genotype and therefore prevent severe and life-threatening toxicity, and to individualize therapy according to TMPT genotype. Follow-up of ALL treatment should preferentially be based on repeated determinations of intracellular active metabolites (6-thioguanine nucleotides) and methylated metabolites in addition to haematological surveillance.

Combination of prednisolone and low dosed dexamethasone exhibits greater in vitro antileukemic activity than equiactive dose of prednisolone and overcomes prednisolone drug resistance in acute childhood lymphoblastic leukemia

INTRODUCTION

Glucocorticoids, particularly prednisone/ prednisolone and dexamethasone, play a prominent role in the treatment of pediatric patients with acute lymphoblastic leukemia due to their ability to induce apoptosis in susceptible cells. Current therapeutic protocols use prednisone for both the prophase and the induction phase of the therapy because the greater antileukemic activity of dexamethasone is compromised by its high frequency of serious adverse reactions.

AIM

To compare, for the first time, the in vitro antileukemic activity of prednisolone alone to that of a combination of prednisolone and dexamethasone using dexamethasone at a very low and presumably safe dosage (1/50 w/w).

METHODS

Lymphoblasts were isolated from bone marrow and/or blood samples from children with newly diagnosed acute lymphoblastic leukemia. The cytotoxic activity of prednisolone, dexamethasone and the prednisolone/dexamethasone combination against isolated leukemia cells was analyzed using the MTT cytotoxicity assay.

RESULTS

We observed differences in the in vitro antileukemic activity of prednisolone and dexamethasone in 21% of the tested patients. 3% of the children were prednisolone sensitive but dexamethasone resistant, while 18% were prednisolone resistant and dexamethasone sensitive. 32% were sensitive to both glucocorticoids and 18% were resistant to both. Cells from patients with good in vivo responses to prednisone monotherapy were more responsive to prednisolone in vitro than were cells from patients with poor prednisone responses (P<0.07). Importantly, we demonstrated that the use of even a minimal dose (1/50 w/w) of dexamethasone with prednisolone dramatically increases the in vitro anti-leukemic activity of prednisolone (P<0.0006).

CONCLUSION

The high inter-individual variability of acute lymphoblastic leukemia responses to glucocorticoids suggest that either patients should be selected for prednisone or dexamethasone treatment on the basis of predictive biomarkers or that prednisone should be used directly in combination with a very low and safe dose of dexamethasone to potentiate its antileukemic activity. The latter option is likely to be cheaper and more efficient, and therefore warrants further clinical investigation to assess its efficacy and safety in treating childhood acute lymphoblastic leukemia.

Long-term health-related outcomes in survivors of childhood cancer treated with HSCT versus conventional therapy: a report from the Bone Marrow Transplant Survivor Study (BMTSS) and Childhood Cancer Survivor Study (CCSS)

HSCT is being increasingly offered as a curative option for children with hematologic malignancies. Although survival has improved, the long-term morbidity ascribed to the HSCT procedure is not known. We compared the risk of chronic health conditions and adverse health among children with cancer treated with HSCT with survivors treated conventionally, as well as with sibling controls. HSCT survivors were drawn from BMTSS (N = 145), whereas conventionally treated survivors (N = 7207) and siblings (N = 4020) were drawn from CCSS. Self-reported chronic conditions were graded with CTCAEv3.0. Fifty-nine percent of HSCT survivors reported ≥ 2 conditions, and 25.5% reported severe/life-threatening conditions. HSCT survivors were more likely than sibling controls to have severe/life-threatening (relative risk [RR] = 8.1, P < .01) and 2 or more (RR = 5.7, P < .01) conditions, as well as functional impairment (RR = 7.7, P < .01) and activity limitation (RR = 6.3, P < .01). More importantly, compared with CCSS survivors, BMTSS survivors demonstrated significantly elevated risks (severe/life-threatening conditions: RR = 3.9, P < .01; multiple conditions: RR = 2.6, P < .01; functional impairment: RR = 3.5, P < .01; activity limitation: RR = 5.8, P < .01). Unrelated donor HSCT recipients were at greatest risk. Childhood HSCT survivors carry a significantly greater burden of morbidity not only compared with noncancer populations but also compared with conventionally treated cancer patients, providing evidence for close monitoring of this high-risk population.

NCI First International Workshop on the Biology, Prevention, and Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation: report from the Committee on Disease-Specific Methods and Strategies for Monitoring Relapse following Allogeneic Stem Cell Transplantation. Part I: Methods, acute leukemias, and myelodysplastic syndromes

Relapse has become the major cause of treatment failure after allogeneic stem cell transplantation. Outcome of patients with clinical relapse after transplantation generally remains poor, but intervention prior to florid relapse improves outcome for certain hematologic malignancies. To detect early relapse or minimal residual disease, sensitive methods such as molecular genetics, tumor-specific molecular primers, fluorescein in situ hybridization, and multiparameter flow cytometry (MFC) are commonly used after allogeneic stem cell transplantation to monitor patients, but not all of them are included in the commonly employed disease-specific response criteria. The highest sensitivity and specificity can be achieved by molecular monitoring of tumor- or patient-specific markers measured by polymerase chain reaction-based techniques, but not all diseases have such targets for monitoring. Similar high sensitivity can be achieved by determination of donor chimerism, but its specificity regarding detection of relapse is low and differs substantially among diseases. Here, we summarize the current knowledge about the utilization of such sensitive monitoring techniques based on tumor-specific markers and donor cell chimerism and how these methods might augment the standard definitions of posttransplant remission, persistence, progression, relapse, and the prediction of relapse. Critically important is the need for standardization of the different residual disease techniques and to assess the clinical relevance of minimal residual disease and chimerism surveillance in individual diseases, which in turn, must be followed by studies to assess the potential impact of specific interventional strategies.

How and why minimal residual disease studies are necessary in leukemia: a review from WP10 and WP12 of the European LeukaemiaNet

Resistance to therapeutic agents is a major factor in the failure of cancer treatments. In leukemia, the resistant cells remaining in the bone marrow and/or peripheral blood constitute minimal residual disease and are detectable by highly sensitive assays when the patient appears to be in complete remission. Early detection of the expansion of residual cells permits clinical intervention with the aim of reversing the proliferation of resistant leukemic cells. Therefore, accurate and precise measurement of minimal residual disease can greatly enhance optimization of oncology patients' clinical management. This notion is supported by a large body of data among chronic myeloid leukemia patients, but minimal residual disease detection and monitoring is increasingly applied to other types of leukemia, and is starting to be a factor in decision-making for some therapeutic trials in childhood acute lymphoblastic leukemia. Here, from the solid ground of minimal residual disease detection in chronic myeloid leukemia, the current state of the art and development of molecular techniques in other leukemias and the growing field of multiparameter flow cytometry are reviewed in two separate parts reporting on the respective advances, advantages and pitfalls of these emerging methods.

Insertional oncogenesis in 4 patients after retrovirus-mediated gene therapy of SCID-X1

Previously, several individuals with X-linked SCID (SCID-X1) were treated by gene therapy to restore the missing IL-2 receptor gamma (IL2RG) gene to CD34+ BM precursor cells using gammaretroviral vectors. While 9 of 10 patients were successfully treated, 4 of the 9 developed T cell leukemia 31-68 months after gene therapy. In 2 of these cases, blast cells contained activating vector insertions near the LIM domain-only 2 (LMO2) proto-oncogene. Here, we report data on the 2 most recent adverse events, which occurred in patients 7 and 10. In patient 10, blast cells contained an integrated vector near LMO2 and a second integrated vector near the proto-oncogene BMI1. In patient 7, blast cells contained an integrated vector near a third proto-oncogene,CCND2. Additional genetic abnormalities in the patients' blast cells included chromosomal translocations, gain-of-function mutations activating NOTCH1, and copy number changes, including deletion of tumor suppressor gene CDKN2A, 6q interstitial losses, and SIL-TAL1 rearrangement. These findings functionally specify a genetic network that controls growth in T cell progenitors. Chemotherapy led to sustained remission in 3 of the 4 cases of T cell leukemia, but failed in the fourth. Successful chemotherapy was associated with restoration of polyclonal transduced T cell populations. As a result, the treated patients continued to benefit from therapeutic gene transfer.

Insertional oncogenesis in 4 patients after retrovirus-mediated gene therapy of SCID-X1

Previously, several individuals with X-linked SCID (SCID-X1) were treated by gene therapy to restore the missing IL-2 receptor gamma (IL2RG) gene to CD34+ BM precursor cells using gammaretroviral vectors. While 9 of 10 patients were successfully treated, 4 of the 9 developed T cell leukemia 31-68 months after gene therapy. In 2 of these cases, blast cells contained activating vector insertions near the LIM domain-only 2 (LMO2) proto-oncogene. Here, we report data on the 2 most recent adverse events, which occurred in patients 7 and 10. In patient 10, blast cells contained an integrated vector near LMO2 and a second integrated vector near the proto-oncogene BMI1. In patient 7, blast cells contained an integrated vector near a third proto-oncogene,CCND2. Additional genetic abnormalities in the patients' blast cells included chromosomal translocations, gain-of-function mutations activating NOTCH1, and copy number changes, including deletion of tumor suppressor gene CDKN2A, 6q interstitial losses, and SIL-TAL1 rearrangement. These findings functionally specify a genetic network that controls growth in T cell progenitors. Chemotherapy led to sustained remission in 3 of the 4 cases of T cell leukemia, but failed in the fourth. Successful chemotherapy was associated with restoration of polyclonal transduced T cell populations. As a result, the treated patients continued to benefit from therapeutic gene transfer.

Superiority of allogeneic hematopoietic stem-cell transplantation compared with chemotherapy alone in high-risk childhood T-cell acute lymphoblastic leukemia: results from ALL-BFM 90 and 95

PURPOSE

The role of hematopoietic stem-cell transplantation (SCT) in first complete remission (CR1) for children with very high-risk (VHR) acute lymphoblastic leukemia (ALL) is still under critical discussion.

PATIENTS AND METHODS

In the ALL-Berlin-Frankfurt-Münster (BFM) 90 and ALL-BFM 95 trials, 387 patients were eligible for SCT if there was a matched sibling donor (MSD). T-cell ALL (T-ALL) patients with poor in vivo response to initial treatment represented the largest homogeneous subgroup within VHR patients.

RESULTS

Of 191 high-risk (HR) T-ALL patients, 179 patients (94%) achieved CR1. Twenty-three patients received an MSD-SCT. Furthermore, in trial ALL-BFM 95, eight matched unrelated donors (MUDs) and five mismatched family donors (MMFDs) were used. The median time to SCT was 5 months (range, 2.4 to 10.8 months) from diagnosis. The 5-year disease-free survival (DFS) was 67% +/- 8% for 36 patients who received an SCT in CR1 and 42% +/- 5% for the 120 patients treated with chemotherapy alone having an event-free survival time of at least the median time to transplantation (Mantel-Byar, P = .01). Overall survival (OS) rate for the SCT group was 67% +/- 8% at 5 years, whereas patients treated with chemotherapy alone had an OS rate of 47% +/- 5% at 5 years (Mantel-Byar, P = .01). Outcome of patients who received MSD-SCT versus MUD-/MMFD-SCT was comparable (DFS, 65% +/- 10% v 69% +/- 13%, respectively). However, relapses only occurred after MSD-SCT (eight of 23 patients), whereas treatment-related mortality only occurred after MUD-/MMFD-SCT (four of 13 patients).

CONCLUSION

SCT in CR1 is superior to treatment with chemotherapy alone for childhood HR-T-ALL.