Thesis (Ph.D.) - Cairo University - National Cancer Institute - Department of Pediatric Oncology

Purpose: To evaluate the frequency of intrachromosomal amplification of chromosome 21(iAMP21) in pediatric patients with B-cell precursor acute lymphoblastic leukemia, to study its relation to clinical as well as biological features of the patients and to assess its prognostic significance. Methods: Pediatric patients with B-cell precursor acute lymphoblastic leukemia (BCP-ALL), who were treated at children cancer hospital Egypt 57357 from the year 2009 to 2011 on St. Jude total study XV protocol were retrospectively screened with ETV6/RUNX1-specific fluorescent in situ hybridization (FISH) probe for the presence of iAMP21. Results: In total, 518 patients were included. iAMP21 was found in 2% of the patients. The median age for iAMP21patients was 6.7 years and the median value of white blood cell count was 6.2 x 10³/mL. None of the patients had Pro-B immunophenotype. About 44% of the patients with iAMP21 had slow early response compared to 17% in the no iAMP21 group (p =0.031). Among iAMP21 patients, those with negative MRD at the end of the induction and received intermediate risk treatment didn't have relapses. On the other hand, 2 out of the 5 patients who received the low risk treatment had relapses despite MRD negativity at the end of the induction. Conclusion: The presence of iAMP21 was related to slow early response to induction treatment and was likely associated with lower RFS compared to patients without iAMP21 (66.7±15.7% v 84.7±1.7%; p=0.205 respectively). So, those patients will benefit from receiving more intensive chemotherapy regimens

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