Tehran University of Medical Sciences Basic & Clinical Cancer Research 2228-6527 3 2 2016 10 09 2 6 EN Asghar Ramyar Department of Hematology and Oncology of Children’s Medical Center, Tehran University of Medical Sciences, Tehran, Iran Asghar Aghamohammadi Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children’s Medical Center, Tehran University ofMedical Sciences, Tehran, Iran Hossein Mozdarani Department of Medical Genetics, School of Medical Sciences, Tarbiat Modares University, Tehran, Iran Majid Mahmoodi Cancer Research Center, Tehran University of Medical Sciences, Tehran, Iran Cyrus Azimi Genetics Group, Cancer Research Center, Cancer Institute,Tehran University of Medical Sciences, Tehran, Iran Zahra Safari Cancer Research Center, Tehran University of Medical Sciences, Tehran, Iran Hassan-Ali Nedaei Radiotherapy Oncology Department, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran Fareedeh Farzanfar Genetics Group, Cancer Research Center, Cancer Institute,Tehran University of Medical Sciences, Tehran, Iran Nima Rezaei Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children’s Medical Center,Tehran University of Medical Sciences, Tehran, Iran Majid Asadi-Shekaari Neuroscience Research Center, Kerman University of Medical Sciences, Kerman, Iran Mahbod Esfahani Radiotherapy Oncology Department, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran Seyed Kazem Hosseini Cancer Research Center, Tehran University of Medical Sciences, Tehran, Iran Mahdi Yazdani Radiotherapy Oncology Department, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran Hassan Abolhassani Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children’s Medical Center, Tehran University of Medical Sciences, Tehran, Iran Fatemeh Khalesi Radiotherapy Oncology Department, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran Mohamad Ali Mohagheghi Cancer Research Center, Tehran University of Medical Sciences, Tehran, Iran 2011 10 30 2011 10 30 Background: Acute lymphoblastic leukemia (ALL) constitutes a heterogeneous group of diseases characterized by abnormal proliferation and accumulation of immature lymphoblasts arrested at various differentiation stages. Increasing evidence suggests that chromosomal defects are present in these patients. The aim of this study is to investigate the chromosomal radiosensitivity in a group of ALL patients. Methods: To analyze chromosomal radiosensitivity of ALL patients, lymphocytes of 20 patients were cultured followed by exposure to γ-ray irradiation to detect the chromosomal aberrations as an indicator of radiosensitivity. Cells were scored for the number of aberrations (chromatid breaks, chromatid gaps, chromosome breaks, chromosome gaps and chromatid exchanges). Results were compared with healthy individuals, and ataxia telangiectasia (AT) patients as positive control. Results: On average number of aberrations in ALL patients was significantly higher than that in healthy controls.  We found 65% of ALL patients appeared to be susceptible to in vitro irradiation. Chromosomal radiosensitivity of 35% patients was not different from healthy donors. Ataxia telangiectasia patients showed the highest degree of lymphocyte radiosensitivity. The results also indicate that there is a good correlation between the two assays, G2 and G0, using the same blood sample for both assays. Conclusion: According to the result, we concluded that most of the ALL patients are sensitive to ionizing radiation and therefore should be protected from unnecessary diagnostic and therapeutic procedures using ionizing radiation. https://bccr.tums.ac.ir/index.php/bccrj/article/view/12 https://bccr.tums.ac.ir/index.php/bccrj/article/download/12/11