Background: It is reported that high frequency of chromosomal aberrations in peripheral blood lymphocytes of individuals is a marker of cancer predisposition. The aim of this study was to investigate the in vitro frequency of chromosomal damage in lymphocytes of patients with head and neck cancer against gamma irradiation compared with those in healthy individuals. Methods: In a case and control study, peripheral blood lymphocytes of 101 patients with head and neck cancer were collected before the onset of radiotherapy. Lymphocytes of 40 healthy individuals were also collected as controls. Head and neck cancer patients and the control group were consecutively recruited between April 2012 and February 2015 from Clinics of Cancer Institute, Imam Khomeini Hospital, Tehran, Iran. Lymphocytes of patients or control group were cultured and exposed to gamma radiation in G2- and G0- phase of the cell cycle. The induced chromosomal aberrations such as chromosome and chromatid breakages, chromosome and chromatid gaps, chromatid exchanges and micronuclei were scored in one-hundred metaphase cells of each individual. The mean of each chromosomal aberration was compared in patient and control groups. Early and late tissue reactions were scored during radiotherapy treatment or thereafter. Results: There was no significant difference in demographic characterization between the two study groups. The frequency of radiation- induced G2 aberrations in lymphocytes of patients was significantly higher than in those of healthy donors (P= 0.001 for chromosomal breaks). The frequency of radiation-induced micronuclei in G0 assay was also higher in patients than in those in controls (P= 0.05). The results also indicate that there is no correlation between the two assays. No significant correlation was also observed between aberration frequencies in lymphocytes and the degree of both early and late normal tissue reactions. Conclusion: The results indicate that the in vitro chromosomal radiosensitivity of peripheral blood lymphocytes of patients with head and neck cancer against gamma irradiation was significantly higher than that in healthy individuals.
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