Relapse is the most common cause of treatment failure in pediatric acute lymphoblastic leukemia (ALL) and is often difficult to predict. To explore the prognostic impact of recurrent DNA copy number abnormalities on relapse, we performed high-resolution genomic profiling of 34 paired diagnosis and relapse ALL samples. Recurrent lesions detected at diagnosis, including PAX5, CDKN2A and EBF1, were frequently absent at relapse, indicating that they represent secondary events that may be absent in the relapse-prone therapy-resistant progenitor cell. In contrast, deletions and nonsense mutations in IKZF1 (IKAROS) were highly enriched and consistently preserved at the time of relapse. A targeted copy number screen in an unselected cohort of 131 precursor B-ALL cases, enrolled in the dexamethasone-based Dutch Childhood Oncology Group treatment protocol ALL9, revealed that IKZF1 deletions are significantly associated with poor relapse-free and overall survival rates. Separate analysis of ALL9-treatment subgroups revealed that non-high-risk (NHR) patients with IKZF1 deletions exhibited a B12-fold higher relative relapse rate than those without IKZF1 deletions. Consequently, IKZF1 deletion status allowed the prospective identification of 53% of the relapse-prone NHR-classified patients within this subgroup and, therefore, serves as one of the strongest predictors of relapse at the time of diagnosis with high potential for future risk stratification.

Response to therapy as determined by minimal residual disease (MRD) is currently used for stratification in treatment protocols for pediatric acute lymphoblastic leukemia (ALL). However, the large MRD-based medium risk group (MRD-M; 50-60% of the patients) harbors many relapses. We analyzed MRD in 131 uniformly treated precursor-B-ALL patients and evaluated whether combined MRD and IKZF1 (Ikaros zinc finger-1) alteration status can improve risk stratification. We confirmed the strong prognostic significance of MRD classification, which was independent of IKZF1 alterations. Notably, 8 of the 11 relapsed cases in the large MRD-M group (n ¼ 81; 62%) harbored an IKZF1 alteration. Integration of both MRD and IKZF1 status resulted in a favorable outcome group (n ¼ 104; 5 relapses) and a poor outcome group (n ¼ 27; 19 relapses), and showed a stronger prognostic value than each of the established risk factors alone (hazard ratio (95%CI): 24.98 (8.29-75.31)). Importantly, whereas MRD and IKZF1 status alone identified only 46 and 54% of the relapses, respectively, their integrated use allowed prediction of 79% of all the relapses with 93% specificity. Because of the unprecedented sensitivity in upfront relapse prediction, the combined parameters have high potential for future risk stratification, particularly for patients originally classified as non-high risk, such as the large group of MRD-M patients.

No abstract

Children with acute lymphoblastic leukemia (ALL) and high minimal residual disease (MRD) levels after initial chemotherapy have a poor clinical outcome. In this prospective, single arm, Phase 2 trial, 111 Dutch and Australian children aged 1-18 years with newly diagnosed, t(9;22)-negative ALL, were identified among 1041 consecutively enrolled patients as high risk (HR) based on clinical features or high MRD. The HR cohort received the AIEOP-BFM (Associazione Italiana di Ematologia ed Oncologia Pediatrica (Italy)-Berlin-Frankfurt-Münster ALL Study Group) 2000 ALL Protocol I, then three novel HR chemotherapy blocks, followed by allogeneic transplant or chemotherapy. Of the 111 HR patients, 91 began HR treatment blocks, while 79 completed the protocol. There were 3 remission failures, 12 relapses, 7 toxic deaths in remission and 10 patients who changed protocol due to toxicity or clinician/parent preference. For the 111 HR patients, 5-year event-free survival (EFS) was 66.8% (±5.5) and overall survival (OS) was 75.6% (±4.3). The 30 patients treated as HR solely on the basis of high MRD levels had a 5-year EFS of 63% (±9.4%). All patients experienced grade 3 or 4 toxicities during HR block therapy. Although cure rates were improved compared with previous studies, high treatment toxicity suggested that novel agents are needed to achieve further improvement.

The contribution of genetic predisposing factors to the development of pediatric acute lymphoblastic leukemia (ALL), the most frequently diagnosed cancer in childhood, has not been fully elucidated. Children presenting with multiple de novo leukemias are more likely to suffer from genetic predisposition. Here, we selected five of these patients and analyzed the mutational spectrum of normal and malignant tissues. In two patients, we identified germline mutations in TYK2, a member of the JAK tyrosine kinase family. These mutations were located in two adjacent codons of the pseudokinase domain (p.Pro760Leu and p.Gly761Val). In silico modeling revealed that both mutations affect the conformation of this autoregulatory domain. Consistent with this notion, both germline mutations promote TYK2 autophosphorylation and activate downstream STAT family members, which could be blocked with the JAK kinase inhibitor I. These data indicate that germline activating TYK2 mutations predispose to the development of ALL.

Monitoring of BCR-ABL transcripts has become established practice in the management of chronic myeloid leukemia. However, nucleic acid amplification techniques are prone to variations which limit the reliability of real-time quantitative PCR (RQ-PCR) for clinical decision making, highlighting the need for standardization of assays and reporting of minimal residual disease (MRD) data. We evaluated a lyophilized preparation of a leukemic cell line (K562) as a potential quality control reagent. This was found to be relatively stable, yielding comparable respective levels of ABL, GUS and BCR-ABL transcripts as determined by RQ-PCR before and after accelerated degradation experiments as well as following 5 years storage at À201C. Vials of freeze-dried cells were sent at ambient temperature to 22 laboratories on four continents, with RQ-PCR analyses detecting BCR-ABL transcripts at levels comparable to those observed in primary patient samples. Our results suggest that freeze-dried cells can be used as quality control reagents with a range of analytical instrumentations and could enable the development of urgently needed international standards simulating clinically relevant levels of MRD.

Clinically and genetically atypical T-cell prolymphocytic leukemia underlines the relevance of a multidisciplinary diagnostic approach Haematologica 2007; 92:(3) e34-e36 Prolymphocytic leukemia (PLL) is a rare clonal lymphoproliferative disorder of mature lymphocytes. The disease originates from B lymphocytes in approximately 80% of cases and from T lymphocytes in 20% of cases. 1 B-PLL and T-PLL are both characterized by an aggressive clinical course with splenomegaly, and a high WBC count. However, generalized lymphadenopathy and cutaneous involvement are rare in B-PLL, while present in ~25% of cases with T-PLL. 1,2 We report a patient with T-PLL with an unusual clinical presentation and relatively indolent clinical course in whom a translocation was found, which was previously described in B-PLL.A 61-year-old man presented with a 2-year history of asymptomatic red raised skin lesions, starting with a few lesions on the back, and gradually progressing until it became almost generalized. On a lesional skin biopsy taken at another clinic 4 months after the first symptoms developed, an initial diagnosis of lichen nitidus was suggested. The patient had no history of skin diseases. There was no pruritus, fever, night sweats, or weight loss. Dermatological examination at our hospital demonstrated numerous erythematous non-scaling papules on the trunk, extremities and behind the ears (Figure 1). The face, palms, and soles were not involved. General physical examination demonstrated cervical and inguinal lymphadenopathy but no hepatosplenomegaly.Computed tomography (CT) showed generalized lymphadenopathy and mild splenomegaly.Laboratory examination revealed a white blood cell (WBC) count of 61X10 9 /L, with 85% lymphocytes, 11% neutrophils, 1% eosinophils, and 3% monocytes. The hemoglobin (Hb) level was 15.2 g/dL and platelet count 98 x 109/L. Biochemistry revealed a slightly elevated lactate dehydrogenase (LDH) level of 567 U/L. Serological analysis of human T cell leukemia virus type 1 (HTLV-I) was negative. Peripheral blood smear showed 91% medium sized lymphoid cells with light grey, sometimes vacuolated cytoplasm, but without cytoplasmic granules (Figure 2A). The nucleus was round or oval shaped and some nuclei showed indentation. An occasional nucleolus was present. The bone marrow smears showed all hematopoietic cell lineages at different stages of maturation and infiltration with lymphoid cells, morphologically similar to the peripheral blood lymphoid cells.Histologic examination of a later skin biopsy showed various patches of non-epidermotropic dermal infiltrates, composed of lymphocytes admixed with Langerhans cells and histiocytes ( Figure 2B -T cells ( Figure 2B; insert). Examination of a bone marrow biopsy demonstrated focal infiltration of small to medium-sized T cells with similar morphology and immunophenotype as those found in skin and peripheral blood.Immunophenotypic analysis of peripheral blood revealed a large population (83% of total leukocytes) of aberrant T cells with the immunophenotype CD...

10017 Background: Bosutinib is a tyrosine kinase inhibitor (TKI), approved for adults with Philadelphia Chromosome (Ph+) CML; at the standard initial dose of 400 mg/day in ND patients, and 500 mg/day in resistant/intolerant (R/I) patients, administered orally once daily (QD) with food. Compared to the TKIs already approved in pediatrics, bosutinib has a different tolerability profile, and preclinical data suggest that longitudinal growth is potentially less impaired. Study NCT04258943 is an international, open-label, phase I/II trial, sponsored by the Erasmus Medical Center and the Children's Oncology Group, and funded by Pfizer Inc. The phase II arm enrolled ND patients, as well as R/I ones. The latter are not included in this analysis. Methods: ND patients aged 1-18 years with chronic phase CML, without evidence for organ toxicities, were enrolled. Main exclusion criteria included known T315I or V299L BCR-ABL1 mutations, and use of proton pump inhibitors and CYP3A inducers/inhibitors. The primary objectives of the phase II part of the study were to assess the safety and pharmacokinetics (PK) of bosutinib at the recommended phase II dose, which is body surface area adjusted, and consists of 300 mg/m2 QD for ND patients (max 500 mg/day), as determined in the phase I part of the study. Based on regulatory authorities requirements, at least 35 patients have to be enrolled in phase II, with a total of 50-60 patients in phase I and II combined. This allows for pooled AE rates to be estimated with a maximum standard error of 0.071 and 0.065, respectively. Results: On 20/12/2022, 25 ND patients were screened, and 24 were enrolled: 15 males, median age 13 years (range: 5-17). The median follow up was 14 (range: 0.9-31) months. The most common non-hematological adverse events (AEs) were diarrhea (n = 16, Grade (Gr) ≤ 2 = 13), abdominal pain (n = 10, Gr ≤ 2 = 10), and nausea/vomiting (n = 8/8, Gr ≤ 2 = 7/8). Most common hematological AEs included platelet count decrease (n = 11, Gr ≤ 2 = 5), and anemia (n = 10, Gr ≤ 2 = 4). At 6 and 12 months, the cumulative incidence of Major Cytogenetic Response (MCyR) was 85% (95%CI 49%-96%) and 92.5% (95%CI 39%-99%), while for Complete CyR it was 77% (47%-91%) and 88.3% (95%CI 55%-98%), and for Major Molecular Response it was 23% (95%CI 7%-46%) and 30% (95%CI 10%-54%), respectively. Three patients permanently discontinued bosutinib due to intolerance, four due to unsatisfactory response per investigator’s judgment, 17 were still on treatment at time of dataset lock. Conclusions: Bosutinib was well tolerated, despite common grade 1-2 gastrointestinal AEs. The preliminary efficacy seems comparable to published data from other second generation TKIs in children and to ND adult patients treated with bosutinib. Clinical trial information: NCT04258943 .