The value of adding rituximab to chemotherapy in children with aggressive B-cell non-Hodgkin lymphoma (B-NHL) is still insufficiently studied. We enrolled 231 patients [mean age 9 years old (range 2-17); male:female ratio 3Á4:1] with Burkitt (BL, 179 patients, 76Á7%), diffuse large B-cell (32 patients, 14%), primary mediastinal B-cell (14 patients, 6%), and other (6 patients, 2Á6%) B-cell lymphomas in a prospective study of immunochemotherapy. Stages were I-II in 32% and III-IV in 68% of the patients. Four doses of 375 mg/m 2 rituximab were added to the Berlin-Frankfurt-Munster-NHL-90-like chemotherapy, with methotrexate being reduced or omitted in the first 2 induction blocks. The complete remission rate was 100% in limited-stage and 91Á4% in advanced-stage patients. Five advanced-stage patients (2Á2%) died in induction and 1 patient with stage 2 B-NHL died in remission; 11 patients in the high-risk group progressed on therapy (3 non-BL are alive after salvage) and 5 relapsed. Sixteen patients (9Á7%) with advanced stage disease proceeded to transplant. With a median follow-up of 46 months, 98Á5 AE 1% of patients with limited disease and 88Á1 AE 2% (88Á1% in Risk Group 3; 82Á6% in Risk Group 4) in advanced stages are alive. This study confirmed that combined immunochemotherapy for B-lymphomas is highly effective in children, despite reducing the intensity of the induction blocks.

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Retroelements (RE) have been proposed as important players in cancerogenesis. Different cancer types are characterized by a different level of tumor-specific RE insertions. In previous studies, small cohorts of hematological malignancies, such as acute myeloid leukemia, multiple myeloma, and chronic lymphocytic leukemia have been characterized by a low level of RE insertional activity. Acute lymphoblastic leukemia (ALL) in adults and childhood acute leukemias have not been studied in this context. We performed a search for new RE insertions (Alu and L1) in 44 childhood ALL, 14 childhood acute myeloid leukemia, and 14 adult ALL samples using a highly sensitive NGS-based approach. First, we evaluated the method sensitivity revealing the 1% detection threshold for the proportion of cells with specific RE insertion. Following this result, we did not identify new tumor-specific RE insertions in the tested cohort of acute leukemia samples at the established level of sensitivity. Additionally, we analyzed the transcription levels of active L1 copies and found them increased. Thus, the increased transcription of active L1 copies is not sufficient for overt elevation of L1 retrotranspositional activity in leukemia.

No abstract

Lymphoblastic lymphoma (LBL) is the second most common non-Hodgkin's lymphoma in childhood. According to modern concepts LBL and acute lymphoblastic leukemia (ALL) are considered as manifestations of the same disease given the similar morphological substrate of the tumor – T and B lymphoblasts. The standard for the treatment of LBL is currently ALL-like riskadapted treatment protocols that allow achieving overall and event-free survival rates of 80–90%. The division into risk groups is based on the stage of the disease and the response to induction therapy. However, the problem of relapse/refractory course of the disease remains a serious problem due to the lack of sufficiently effective therapeutic options. Currently, there is a sufficient amount of clinical data that reliably shows that a number of molecular biological factors can be used to create a new system of into risk groups stratification of patients with LBL. This review focuses on the analysis of various factors that may be responsible for the prognosis of LBL in children.