Legacy data show that approximately 40% of children with acute lymphoblastic leukemia (ALL) were cured with limited antimetabolite-based chemotherapy regimens. However, identifying patients with very-low-risk (VLR) ALL remains imprecise. Patients selected based on a combination of presenting features and a minimal residual disease (MRD) level of <0.01% on day 19 of induction therapy had excellent outcomes with low-intensity treatment. We investigated the impact of MRD levels between 0.001% and <0.01% early in remission induction on the outcome of VLR ALL treated with a low-intensity regimen. Between October 2011 and September 2015, 200 consecutive patients with B-precursor ALL with favorable clinicopathologic features and MRD levels of <0.01%, as assessed by flow cytometry in the bone marrow on day 19 and at the end of induction therapy, received reduced-intensity therapy. The 5-year event-free survival was 89.5% (± 2.2% SE), and the overall survival was 95.5% (± 1.5% SE). The 5-year cumulative incidence of relapse (CIR) was 7% (95% CI, 4% to 11%). MRD levels between 0.001% and <0.01% on day 19 were detectable in 29 patients. These patients had a 5-year CIR significantly higher than that of patients with undetectable residual leukemia (17.2% ± 7.2% vs 5.3% ± 1.7%, respectively; P = .02). Our study shows that children with VLR ALL can be treated successfully with decreased-intensity therapy, and it suggests that the classification criteria for VLR can be further refined by using a more sensitive MRD assay.

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Aggresomes are transient microtubule-dependent inclusion bodies that sequester misfolded proteins and are ultimately removed by autophagy. Here we report the generation of a choroid plexus carcinoma cell line; Children’s Cancer Hospital Egypt (CCHE)-45, which is characterized by the constitutive formation of aggresomes. When examining the autophagy pathway as the main route for aggresomes clearance, CCHE-45 cells displayed increased autophagy flux mediated by MAP1LC3B. MAP1LC3A-Variant1 gene expression was silenced by promoter methylation. Restoring MAP1LC3A-Variant1 expression resulted in the formation of MAP1LC3A positive autophagosmes and the disruption of the aggresomes' vimentin cage independent of MAP1LC3B positive autophagosomes. Our data supports the notion that basal quality control autophagy and vimentin cage clearance in CCHE-45 are mediated by MAP1LC3A. Hence we propose that absence of MAP1LC3A disrupts the autophagic pathway and leads to the failure of aggresome vimentin cage degradation. Consequently, this could represent a targetable pathway in autophagy-dependent cancers.

10044 Background: With modern risk directed therapy, >80% of children with acute lymphoblastic leukemia (ALL) in western countries are cured. The 5-year event free survival (EFS) and relapse free survival (RFS) of pediatric ALL patients in Egypt were 65% and 75% respectively in a previous study using an intensive treatment protocol for all patients. Aim: To improve cure rates of Egyptian children with ALL using risk adapted therapy. Methods: From July 2007 to December 2010, 706 patients aged 1-18 years with newly diagnosed ALL were treated at Children Cancer Hospital Egypt with a risk directed ALL protocol adopted from St Jude Total Study XV. Results: B-precursor phenotype was encountered in 75.8% and T-cell in 24.2%. Based on initial presentation and response to therapy measured by minimal residual disease (MRD), 42.6%, 45.8% and 11.6% of the patients were classified as low, intermediate and high risk respectively. The 5-year RFS and EFS were 88.2 ± 1.5% and 76.5 ± 1.7% respectively. Adverse events included 4.4% induction deaths, 2.5% failure to achieve induction remission (1.4% remained refractory), 6.8% deaths in remission, 9.2% relapses (3.1% hematological, 1.8% combined hematological and CNS, 4% isolated CNS, 0.3% isolated testicular), 0.9% abandonment of therapy and one patient had secondary myeloid leukemia. The median follow up for patients alive in CR was 43months (range 24–65). The 5-year RFS of the low, intermediate and high risk groups were 92.2 ± 2.4%, 85.3 ± 2.2% and 82.7 ± 4.8% respectively (p=0.001), while the 5-year EFS were 87.6 ± 2.5%, 78.2 ± 2.5% and 57.9 ± 5.7% respectively (p<0.001). Prognostic factors that had statistically significant unfavorable impact on both EFS and RFS by univariate analysis were age ≥10 years, TLC ≥100x109/L, T-cell phenotype, risk groups, MRD d42 ≥1% and MRD W7 ≥0.1%, while MRD d15 ≥1% had statistically significant unfavorable outcome on EFS only. By multivariate analysis, TLC and MRD W7 had prognostic significance on EFS and RFS, MRD d42 on EFS, while MRD d15 had marginal significance on EFS (p=0.055). Conclusions: Risk adapted therapy was effective in improving ALL survival among patients at our institution compared with previous trials, although the outcome remains lower than that in high income countries.