The experimental study of 125I seeds interstitial brachytherapy combined with external beam radiotherapy for lewis lung cancer in C57BL/6 mice

Objective: 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 (15 Gy) alone, and combination of 125I seeds interstitial brachytherapy with external beam radiotherapy (8 Gy). After treatment.the volulne of the tumors was measured every 3 days. The animals were executed, the weight of tumors was measured.tumor control rate was calculated and pathological examination was performed on day 15. The intratumoral micro-vaseular density (MVD) in each group was evaluated by inmmnohistochemical methads. Tumor volume.weight and MVD were compared by one-way ANOVA, student. newlnan-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 brachytherapy group (28.6%). while the difference of tumor weisht was not significant between the former two groups (q=0.50. P>0.05). Immunohistochemistry analysis showed that the MVD value in the four groups wag (23.33 ± 4.84). (17.50 ± 3.67), (11.83 ± 2.14) and (12.67 ± 3.39) / (high power field x 200) regpectively. 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). Conclusions: 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. (authors)