Abstract: OBJECTIVE: To assess the DNA damage by comet assay in cervical cancer patients undergoing radiotherapy. METHODS：Blood samples were collected from 15 cervical cancer patients exposed to radiation at the accumulated dose of 0，10，20，30，40，50，60 Gy. DNA damage was measured by comet assay. RESULTS： Rate of lymphocyte DNA tailing in radiation groups increased significantly compared with to pre-radiation (P<0.01)，showing a linear relationship from 0 to 60 Gy. The regression equation was y =12.133+0.230x，r =0.964 (P<0.05). The tail length showed significant increase in radiation groups compared with pre-radiation (P<0.01). At the accumulated dose of 30 Gy，the tail length reached the peak value. The tail length decreased a little，but remained at a higher level still when dose was higher than 30 Gy, compared to pre-radiation (0 Gy)(P<0.01). There was no dose-effect relationship between tail length and accumulated dose. CONCLUSION：Radiotherapy may induce DNA damage in cervical cancer patients. Evaluation of the radiation- damage by comet assay has a high sensitivity.

Key words: cervical cancer, radiotherapy, comet assay, radiation-induced damage, dose-effect relationship