Feasibility Of Implementation Of Preoperative Radiotherapy By SIB-VMAT In Rabbit Limb Soft Tissue Tumor Model

Objective:To investigate the feasibility of implementation of preoperative volumetric modulated arc radiotherapy (VMAT) using simultaneous integrated boost (SIB) in the tumor site adjacent neurovascular bundles or bones, making a "necrotic zone". Methods:Thirty VX2 soft tissue tumor models were successfully made, two weeks later all tumor models were divided into three groups using random number table:VMAT group (10), IMRT group (10) and control group (10). The tumor site adjacent neurovascular bundles or bones were delivered 4 days a week to a dose of 40Gy in 8 fractions. MR scanning was performed after radiotherapy for all the rabbits, and tumor volumes were measured. One week after the radiotherapy all the rabbits were put to death. Cell apoptosis were determined by using TUN EL and HE method after radiation for all the rabbits. And the expressions of K-i67 were detected by immunohistochemistry for all the rabbits. Results:The tumor growths of the group VMAT and IMRT were significantly slower than that of the control group. The tumor volumes of the group VMAT and IMRT were21.13±2.03 cm3,19.25±2.12 cm3, (P=0.10), but they were significantly smaller than that of the control group. (45.56±4.00 cm3,P<0.01). The expression of Ki-67 antigen reduced significantly while radiotherapy, The expressions of Ki-67 in the group of VMAT and IMRT were(49.88±2.41)%、(52.25±1.83)%, (P=0.43),while they were significantly higher in the control group (P<0.01) The apoptotic index (AI) of radiotherapy group after radiotherapy was 93.25±1.39、92.38±1.30, which was significantly higher than that of the control group(P<0.01). Conclusion:It is feasible to imply preoperative radiotherapy in the rabbit VX2 soft tissue tumor by SIB-VMAT.