A comparison of two immobilization systems for stereotactic body radiation therapy of lung tumors

Purpose: This study aims to compare the efficacy, efficiency and comfort level of two immobilization systems commonly used in lung stereotactic body radiation therapy (SBRT): the Bodyfix and the abdominal compression plate (ACP). Materials and methods: Twenty-four patients undergoing SBRT for medically inoperable stage I lung cancer or pulmonary metastases were entered on this prospective randomized study. All underwent 4DCT simulation with free breathing, the Bodyfix, and the ACP to assess respiratory tumor motion. After CT simulation, patients were randomly assigned to immobilization with either the Bodyfix or the ACP for the actual SBRT treatment. Cone beam CTs (CBCTs) were acquired before and after each treatment to assess intrafraction tumor motion. Setup time and patient comfort were recorded. Results: There were 16 upper lobe, two middle lobe and seven lower-lobe lesions. Both the Bodyfix and the ACP significantly reduced the superior-inferior (SI) and overall respiratory tumor motion compared to free breathing (4.6 and 4.0 vs 5.3 mm; 5.3 and 4.7 vs 6.1 mm, respectively, p < 0.05). The ACP further reduced the SI and overall respiratory tumor motion compared to the Bodyfix (p < 0.05). The mean overall intrafraction tumor motion was 2.3 mm with the Bodyfix and 2.0 mm with the ACP (p > 0.05). The ACP was faster to set up and rated more comfortable by patients than the Bodyfix (p < 0.05). Conclusions: While there is no significant difference between the Bodyfix and ACP in reducing intrafraction tumor motion, the ACP is more comfortable, faster to set up, and superior to the Bodyfix in reducing SI and overall respiratory tumor motion.