超分割和常规放疗Lewis肺癌及后期组织放射生物效应的研究

COMPARISON OF THE RADIATED BIOLOGICAL EFFECTS OF HYPER AND CONVENTIONAL FRACTIONATED IRRADIATION ON LEWIS LUNG CARCINOMA AND LATE NORMAL TISSUE

研究了超分割和常规分割放疗Ｌｅｗｉｓ肺癌和小鼠后肢后期正常组织的损伤效应。超分割采用每日二次（间隔为１０～１２小时），每次剂量２，０Ｇｙ～５．５Ｇｙ；常规方法采用每日一次，每次剂量３．５Ｇｙ～８．５Ｇｙ，均照射８天。正常后期组织损伤以小鼠后肢孪缩为观察指标，５０％小鼠放射７０天后肢体孪缩５ｍｍ两种方法所需的剂量，结果超分割５９Ｇｙ；常规５４Ｇｙ。肿瘤放射效应以特别肿瘤增殖延迟（ＳＴＧＤ）为观察指标，两种方法导致ＳＴＧＤ＝３．１４所需的剂量为等效剂量。结果超分割４２．７５Ｇｙ；常规４４Ｇｙ。超分割放疗可较常规放疗提高治疗增益１２．５％。

AbstractThe biological effects were compared on Lewis lung carcinoma and normaI tissue in mice be-tween hyperfractionated(HF)and conventional fractionated radiation(CF). HF was used twicedaily(interval≥10 hrs),2.0-5. 5 Gy per fraction , and CF once daily,3.5-8. 0 Gy per fraction.The duration of radiotherapy was 8 days in both groups, Leg contracture(LC)of mice served asan end point for late response in normal tissue。 LCD50 was definied as the radiation dose requiredfor 5 mm of leg contracture in 50%of the hind legs of the mice measured at the 70th day after ir-radiation。 LCD50 for HF was 59. 0 Gy and CF, 54. 0 Gy, Specific tumour growth delay(STGD)was taken as an end point for Lewis lung carcinoma。 ED was defined as the radiation dose re-quired for STGD, equal to 3. 14 in two group animals.ED for HF was 42. 75 Gy and CF,44 Gy,Itis concluded that hyperfractionation as compared with conventional radiation can enhanced thera-peutic gain for 12.5%.