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