Evaluation of Cytogenetic Alterations in Peripheral Blood Lymphocytes of Esophageal Cancer Patients Treated with Radiotherapy or Chemoradiotherapy using Cytokinesis-Blocked Micronucleus Assay

The effects of combined radiotherapy (RT) and chemotherapy in the severity of cytogenetic alterations expressed as micronucleus (MN) in peripheral blood lymphocytes of patients treated for esophageal cancer was evaluated. To do this, blood was obtained from 23 and 15 esophageal cancer patients scheduled for chemo-radiotherapy and RT alone, respectively, before, during, and after treatment. Blood samples were cultured in RPMI-1640 complete medium containing 1% phytohemagglutinin and incubated in a CO2 incubator. Cytochalasin-B was added to the cultures at a final concentration of 5μg/ml. Finally, harvesting, slide making, and analysis were performed according to standard procedures. Results indicate that there was no significant difference between the frequencies of MN in lymphocytes of individuals before being treated with RT alone or chemo-radiotherapy. In the middle of treatment, (after 12 fractions of RT) the frequency of MN increased significantly compared with their concurrent pre-treatment samples in both groups (four-fold). However, the frequency of MN observed for RT patients was not significantly different with those received chemo- and radiotherapy. At the end of treatment, (after 24 fractions of radiotherapy) an increase in the MN frequency was observed for chemo-radiation group significantly higher than RT group (P=0.022). Mild increase in MN frequency in lymphocytes of patients receiving chemoradiation only after the completion of treatment course might be indicative of resistance induced by chemotherapeutics to the clastogenic effects of radiation. Therefore, using these agents repeatedly for cancer treatment in combination with radiation might not cause severe adverse biological effects in normal tissues.