Abstract: Purpose : To investigate the difference of repairing DNA breaks in cells of lung cancer patients and it clinical expression. Methods : The cultures of human lymphocytes were t reated with blemycin , and the number of chromatid breaks per cell (b/ c) was recorded. The effect s of patient s with higher and lower DNA repair capability t reated with radiotherapy or chemotherapy were observed. Results : ①Mean value of b/ c in lung cancer patient s was 1. 02 , with standard deviation of 0. 72. Fifty two percent were low DNA repair capability class ; them , 37 % were ext remely low repair capability class. ②Low DNA repair capability class increased remarkably with the groups of increased age ( P < 0. 05) . ③The f requency of recurrence and metastasis in low DNA repair capability class was 31 % , higher than 23 % in normal DNA repair capability class. Of patient s appearing clinical side and toxical effect s , 78 % were those in low DNA repair capability class. Conclusion : DNA repair capability in cells of lung cancer patient s decreased with the increase of age. Low DNA repair capability class is susceptible to recurrence and metastasis , and appearing side toxical effects when t reated with radiotherapy and chemotherapy. DNA repair apability in cells is expected to become a biological marker in individual specific t reatment .

Key words: lung cancer, DNA breaks, repair