Application of abdominal balloon compression combined with four-dimensional computed tomography in three-dimensional radiotherapy for non-small cell lung cancer

Abstract

Objective To compare the size of target volume, amplitudes of movements in different directions, movement vector, dose to the diseased lung, whole lung volume, and setup error between free breathing fixation (method A) and four-dimensional computed tomography (4DCT)-guided abdominal balloon compression fixation (method B), and to demonstrate that the 4DCT-guided abdominal balloon compression fixation is effective in the treatment of non-small cell lung cancer (NSCLC). Methods A retrospective analysis was performed among 80 patients with NSCLC in our hospital. In those patients, 40 received method A and 40 method B. The GTVfree and GTVpress were delineated on the maximum intensity projection (MIP) images of 10 respiratory phases using method A and method B, respectively. The PTVfree and PTVpress were obtained by expansion of the GTVfree and GTVpress, respectively. The paired t test was used to analyze the differences in the PTV, maximum amplitudes of movements in three dimensions, absolute value of the movement vector (|V|), and volume between method A and method B. The treatment planning system was used to compare the V5, V10, V20, and V30 of the diseased lung and the whole lung volume between method A and method B. All patients underwent cone-beam CT (CBCT) scans after positioning. Setup error was obtained by matching the CBCT images with the MIP images in the XVI system based on bone and grayscale values. Results The PTVfree and PTVpress were (283.2±12.74) and (201.8±12.99) cm3, respectively (P=0.002). The maximum amplitudes of movements in the right-left, superior-inferior, and anterior-posterior directions as well as the|V| value were (0.22±0.02), (1.85±0.08), (0.43±0.26), and (1.91±0.27) cm, respectively, for method A, and (0.05±0.01), (0.41±0.03), (0.16±0.16), and (0.44±0.16) cm, respectively, for method B (P=0.120, 0.001, 0.070). The V5, V10, V20, and V30 for the diseased lung and total lung volume were (61.26±4.27)%, (44.52±1.70)%, (28.22±3.13)%, (18.26±5.17)%, and (3556±223.12) cm3, respectively, for method A, and (52.74±4.78)%, (38.76±4.92)%, (23.71±4.03)%, (15.54±3.43)%, and (3376±311.65) cm3, respectively, for method B (P=0.001, 0.003, 0.004, 0.021, 0.004). There was no significant difference in setup error obtained by the XVI system between the two fixation methods (P>0.05). Conclusions Without increasing setup error, abdominal balloon compression can effectively control the lung movement amplitude, reduce the planning target volume, and reduce the radiation dose to the lung in patients with NSCLC. Key words: Abdominal balloon compression; Free Breathe; Carcinoma, non-small cell lung/three-dimensional radiotherapy