Nationwide survey of therapy-related leukemia in childhood in Japan

Mechanisms of Secondary Leukemia Development Caused by Treatment with DNA Topoisomerase Inhibitors

Leukemia is a blood cancer originating in the blood and bone marrow. Therapy-related leukemia is associated with prior chemotherapy. Although cancer therapy with DNA topoisomerase II inhibitors is one of the most effective cancer treatments, its side effects include development of secondary leukemia characterized by the chromosomal rearrangements affecting AML1 or MLL genes. Recurrent chromosomal translocations in the therapy-related leukemia differ from chromosomal rearrangements associated with other neoplasias. Here, we reviewed the factors that drive chromosomal translocations induced by cancer treatment with DNA topoisomerase II inhibitors, such as mobility of ends of double-strand DNA breaks formed before the translocation and gain of function of fusion proteins generated as a result of translocation.

Pediatric Acute Myeloid Leukemia Post Cytotoxic Therapy-Retrospective Analysis of the Patients Treated in Poland from 2005 to 2022

Acute P./myeloid leukemia post cytotoxic therapy (AML-pCT) is rare complication of cancer treatment in childhood. The objective of the study was to identify clinical characteristics and provide an analysis of the outcomes in pediatric AML-pCT. We retrospectively analyzed the data of 40 children with AML-pCT, treated from 2005 to 2020 within the Polish Pediatric Leukemia and Lymphoma Study Group. The most common primary malignancies were acute lymphoblastic leukemia (32.5%) and brain tumors (20%). The median latency period was 2.9 years (range: 0.7-12.9). Probabilities of overall (OS), event-free (EFS), and relapse-free survival (RFS) in the whole cohort were 0.49 ± 0.08, 0.43 ± 0.08, and 0.64 ± 0.10, respectively. Significant improvements in outcomes were observed in patients treated from 2015-2022 (two induction cycles followed by stem cell transplantation-SCT in 69% of patients) compared to 2005-2014 (four induction cycles followed by SCT in 49% of patients). The probability of EFS increased from 0.30 ± 0.10 to 0.67 ± 0.12 (p = 0.07) and RFS increased from 0.46 ± 0.11 to 1.0 (p = 0.01). The poorest outcome (OS and EFS 0.25 ± 0.20) was in AML post brain tumor, mainly due to deaths from toxicities. To conclude, treatment results achieved in patients with AML-pCT treated from 2015-2022, with two induction cycles followed by immediate SCT, were better than those reported by other authors, and comparable to the results in de novo AML.

Recurrent Translocations in Topoisomerase Inhibitor-Related Leukemia Are Determined by the Features of DNA Breaks Rather Than by the Proximity of the Translocating Genes

Topoisomerase inhibitors are widely used in cancer chemotherapy. However, one of the potential long-term adverse effects of such therapy is acute leukemia. A key feature of such therapy-induced acute myeloid leukemia (t-AML) is recurrent chromosomal translocations involving AML1 (RUNX1) or MLL (KMT2A) genes. The formation of chromosomal translocation depends on the spatial proximity of translocation partners and the mobility of the DNA ends. It is unclear which of these two factors might be decisive for recurrent t-AML translocations. Here, we used fluorescence in situ hybridization (FISH) and chromosome conformation capture followed by sequencing (4C-seq) to investigate double-strand DNA break formation and the mobility of broken ends upon etoposide treatment, as well as contacts between translocation partner genes. We detected the separation of the parts of the broken AML1 gene, as well as the increased mobility of these separated parts. 4C-seq analysis showed no evident contacts of AML1 and MLL with loci, implicated in recurrent t-AML translocations, either before or after etoposide treatment. We suggest that separation of the break ends and their increased non-targeted mobility—but not spatial predisposition of the rearrangement partners—plays a major role in the formation of these translocations.

Bone Marrow Surveillance of Pediatric Cancer Survivors Identifies Clones that Predict Therapy-Related Leukemia

PURPOSE

Therapy-related myelodysplastic syndrome and acute leukemias (t-MDS/AL) are a major cause of nonrelapse mortality among pediatric cancer survivors. Although the presence of clonal hematopoiesis (CH) in adult patients at cancer diagnosis has been implicated in t-MDS/AL, there is limited published literature describing t-MDS/AL development in children.

EXPERIMENTAL DESIGN

We performed molecular characterization of 199 serial bone marrow samples from 52 patients treated for high-risk neuroblastoma, including 17 with t-MDS/AL (transformation), 14 with transient cytogenetic abnormalities (transient), and 21 without t-MDS/AL or cytogenetic alterations (neuroblastoma-treated control). We also evaluated for CH in a cohort of 657 pediatric patients with solid tumor.

RESULTS

We detected at least one disease-defining alteration in all cases at t-MDS/AL diagnosis, most commonly TP53 mutations and KMT2A rearrangements, including involving two novel partner genes (PRDM10 and DDX6). Backtracking studies identified at least one t-MDS/AL-associated mutation in 13 of 17 patients at a median of 15 months before t-MDS/AL diagnosis (range, 1.3-32.4). In comparison, acquired mutations were infrequent in the transient and control groups (4/14 and 1/21, respectively). The relative risk for development of t-MDS/AL in the presence of an oncogenic mutation was 8.8 for transformation patients compared with transient. Unlike CH in adult oncology patients, TP53 mutations were only detectable after initiation of cancer therapy. Last, only 1% of pediatric patients with solid tumor evaluated had CH involving myeloid genes.

CONCLUSIONS

These findings demonstrate the clinical relevance of identifying molecular abnormalities in predicting development of t-MDS/AL and should guide the formation of intervention protocols to prevent this complication in high-risk pediatric patients.

Therapy‑related acute myeloid leukemia: A case series

Patients with primary cancer receiving chemotherapy and/or radiotherapy may develop therapy-related acute leukemia (t-AL). Therapy-related acute myeloid leukemia (t-AML) accounts for the majority of these cases and is frequently associated with a variety of cytogenetic and molecular abnormalities. The aim of the present study was to explore the clinical characteristics, treatments and prognosis of patients with t-AML. A total of 272 cases of AML treated at our institution between 2016 and 2020 were reviewed, among which nine cases of t-AML were identified for analysis. All patients had received alkylating or topoisomerase II inhibitor chemotherapy drugs for primary cancer treatment and three patients had received radiotherapy. A total of nine patients had been administered recombinant human granulocyte colony-stimulating factor (G-CSF). The median latency period for the nine patients with t-AML was 25 months (range, 10–240 months). The molecular cytogenetic abnormalities included t(15:17)(q22:q21), inv(16)(p13q22), del(5)(q22), CBFB/MYH11(+), FLT3(+), NARS(+), IDH(+), TET2(+), and TP53(+). Out of nine patients with t-AML, eight received chemotherapy, two of whom underwent HSCT. The median survival time of the nine patients with t-AML was 10 months and the 2-year-survival rate was 44.4%. Greater clarity around the diagnosis and treatment is required to improve the outcomes of patients with t-AML.

Therapy-related Myeloid Neoplasms in Children: A Single-institute Study

Therapy-related myeloid neoplasm (t-MN) in the pediatric population is not well characterized. We studied 12 pediatric patients diagnosed with t-MN in our institution since 2006. The median age at the t-MN diagnoses was 14.8 years (range, 9 to 20 y). The primary malignancies included 9 solid tumors and 3 hematopoietic malignancies. Rhabdomyosarcoma (n=4) was the most common primary malignancy. Five of the 9 patients with solid tumors and all 3 patients with hematopoietic malignancies had primary neoplasms involving bone marrow. The median latency period was 5.2 years (range, 1.8 to 13.8 y). Thrombocytopenia was present in all patients at the t-MN diagnoses. Complete or partial monosomy of chromosome 5 or 7 were the 2 most common cytogenetic abnormalities. A quarter of patients demonstrated a genetic predisposition to t-MN: 1 with Li-Fraumeni syndrome with a germline TP53 R248Q mutation, 1 with Noonan syndrome with a somatic mutation (PTPN11 S502T), and 1 with a constitutive chromosomal translocation [t(X;9)(p22;q34)] and a germline TP53 L130V mutation. Outcomes remain poor. Two patients survived 3 and 5.1 years after hematopoietic stem cell transplantation.

Outcomes of pediatric patients with therapy-related myeloid neoplasms

Long-term outcomes after allogeneic hematopoietic cell transplantation (HCT) for therapy-related myeloid neoplasms (tMNs) are dismal. There are few multicenter studies defining prognostic factors in pediatric patients with tMNs. We have accumulated the largest cohort of pediatric patients who have undergone HCT for a tMN to perform a multivariate analysis defining factors predictive of long-term survival. Sixty-eight percent of the 401 patients underwent HCT using a myeloablative conditioning (MAC) regimen, but there were no statistically significant differences in the overall survival (OS), event-free survival (EFS), or cumulative incidence of relapse and non-relapse mortality based on the conditioning intensity. Among the recipients of MAC regimens, 38.4% of deaths were from treatment-related causes, especially acute graft versus host disease (GVHD) and end-organ failure, as compared to only 20.9% of deaths in the reduced-intensity conditioning (RIC) cohort. Exposure to total body irradiation (TBI) during conditioning and experiencing grade III/IV acute GVHD was associated with worse OS. In addition, a diagnosis of therapy-related myelodysplastic syndrome and having a structurally complex karyotype at tMN diagnosis were associated with worse EFS. Reduced-toxicity (but not reduced-intensity) regimens might help to decrease relapse while limiting mortality associated with TBI-based HCT conditioning in pediatric patients with tMNs.

Effect of Down-Regulation of miR-23b-3p on the Differentiation of Acute Myeloid Leukemia via Wilms Cancer Gene 1

miRNA has always been a hot spot research. We assessed the effect of down-regulation of miR-23b-3p on the differentiation of acute myeloid leukemia (AML). Human AML cell line U937 was divided into blank group, NC group and miR-23b-3p low expression group (transfected with miR-23b-3p inhibitor) and miR-23b-3p followed by analysis of WT1 level and relationship between miR-23b-3p and WT1 by dual luciferase reporter assay. All-trans retinoic acid is used to induce differentiation, and then the morphological changes of cells and CD11b level were detected. When miR-23b-3p level was reduced, WT1 mRNA and protein level was also decreased. Dual luciferase assay showed that miR-23b-3p bound to WT1 3’-UTR. Inhibition of miR-23b-3p significantly decreased cell proliferation. Swiss Giemsa staining showed that most of cells were in the differentiation stage with low miR-23b-3p expression. The differentiation marker CD11b was significantly higher than other groups, indicating that low miR-23b-3p expression can promote cell differentiation and reduce cell proliferation to a certain extent. Under low miR-23b-3p expression, the positive rate of CD11b was significantly increased. Down-regulating miR-23b-3p can inhibit WT1 to a certain extent and promote the differentiation of AML, which provides a guidance for the gene-level treatment of AML.

The acquisition of molecular drivers in pediatric therapy-related myeloid neoplasms

Pediatric therapy-related myeloid neoplasms (tMN) occur in children after exposure to cytotoxic therapy and have a dismal prognosis. The somatic and germline genomic alterations that drive these myeloid neoplasms in children and how they arise have yet to be comprehensively described. We use whole exome, whole genome, and/or RNA sequencing to characterize the genomic profile of 84 pediatric tMN cases (tMDS: n = 28, tAML: n = 56). Our data show that Ras/MAPK pathway mutations, alterations in RUNX1 or TP53, and KMT2A rearrangements are frequent somatic drivers, and we identify cases with aberrant MECOM expression secondary to enhancer hijacking. Unlike adults with tMN, we find no evidence of pre-existing minor tMN clones (including those with TP53 mutations), but rather the majority of cases are unrelated clones arising as a consequence of cytotoxic therapy. These studies also uncover rare cases of lineage switch disease rather than true secondary neoplasms.

Therapy-related acute myeloid leukemia following treatment for cancer in childhood: A population-based registry study

BACKGROUND

Therapy-related acute myeloid leukemia (t-AML) is defined as AML that develops after exposure to cytotoxic chemotherapy and/or radiation therapy. There is a paucity of available literature, particularly in regard to t-AML following childhood cancer. Our aim was to describe the risk of t-AML among children treated for other cancers and their subsequent survival.

PROCEDURE

We utilized data from the population-based Australian Childhood Cancer Registry to examine all childhood patients (<15 years at diagnosis) treated with chemotherapy and/or radiotherapy for cancers other than AML who received a subsequent diagnosis of AML between 1983 and 2014. Standardized incidence ratios (SIRs) were calculated to approximate the relative risk of being diagnosed with AML compared to the general population. Estimates of 5-year observed survival were obtained using the Kaplan-Meier method, with differences determined by the log-rank test.

RESULTS

Fifty-eight of 11,753 patients in the study cohort (0.5%) were diagnosed with t-AML, an almost 50-fold higher risk than expected (SIR = 45.6, 95% confidence interval [CI] = 35.3-59.0). Five-year observed survival from the date of t-AML diagnosis was 31.2% (95% CI = 19.6-43.5%). A significant survival advantage was found for patients who underwent hematopoietic stem cell transplantation (HSCT) following diagnosis of t-AML, with a 5-year survival of 52.4% (29.7-70.9%) compared to 5.7% (0.4-22.6%) for those who did not have HSCT (P < 0.001).

CONCLUSIONS

Although rare, t-AML is an important potential late effect of childhood cancer therapy. Prognosis is generally poor, with HSCT offering some survival benefit.