The Experimental Study Of ¹²⁵i Seeds Interstitial Brachytherapy Combined With External Beam Radiotherapy For Lewis Lung Cancer In C57bl/6 Mice

The experimental study of ¹²⁵I seeds interstitial brachytherapy combined with external beam radiotherapy for Lewis lung cancer in C57BL/6 miceObjective: The purpose of this study was to investigate the efficacy of ¹²⁵I seeds interstitial brachytherapy combined with external beam radiotherapy for lung neoplasm.Methods: Each set of six C57BL/6 mice bearing Lewis tumor was stratified into four groups on day 1 :vehicle control, ¹²⁵I seeds interstitial brachytherapy alone, external beam radiotherapy(15Gy) alone, and combination of ¹²⁵I seeds interstitial brachytherapy with external beam radiotherapy(8Gy). After treatment, the volume of the tumors was measured every 3 day. The animals were executed, the weight of tumors was measured, tumor control rate was calculated and pathological examinati- on was performed on day 15. The intratumor micro-vascular density (MVD) in each group was evaluated by immunohistochemical methods. Tumor volume, weight and MVD were compared by one-way ANOVA, student-newman-keuls(SNK)-q analysis.Results: Comparing with control group, the other three groups had significant inhibiting effect on the growth of Lewis tumor(q =11.06,17.13,16.31, all P <0.05). Tumor growth inhibition in external beam radiotherapy alone group and combination group (50.9% and 48.4% respectively) were higher than ¹²⁵I seeds interstitial brachyt- herapy group (28.6%), while the difference was not significant between the former two groups(q =0.50,P >0.05). Immunohistochemistry analysis showed that the MVD values in the four groups was (23.33±4.84), ( 17.50±3.67), ( 11.83±2.14) and ( 12.67±3.39)/(high power field×200) respectively. The MVD value of ¹²⁵I seeds interstitial brachytherapy alone group was much lower than that of control group, and higher than combination group (q =3.92 and 3.25, both P <0.05). Additionally, there was no significant difference between external beam radiotherapy alone group and combination group (q =0.57, P >0.05).Conclusion: Radiotherapy can significantly reduce the MVD values of tumor and inhibit tumor growth through the mechanisms of antiangiogenesis. The combined treatment of lung tumors with implanted 125I seeds and external beam irradiation can decrease the total dose of the external beam irradiation and, hence, offer the possibility of considerable dose sparing of normal tissues without compromising local tumor control rates.