Abstract:

Objective To investigate the dosimetric advantages of respiratory ⁃triggered prospective gating in stereotactic body radiation therapy（SBRT）for early⁃stage non⁃small⁃cell lung cancer（NSCLC）. Methods A total of 21 patients with pathologically confirmed early ⁃stage NSCLC were selected and received free ⁃breathing 3D ⁃ CT，4D⁃CT cine mode and end⁃expiratory prospective respiratory⁃triggered axial⁃R mode scans，respectively. With FFF，VMAT and SBRT technology under the same condition，four corresponding plans，prospective gating（Planpro）， 30% ~ 70% temporal retrospective gating（Plan30⁃70），motion enveloped method（Planall）and conventional population margin⁃based 3D⁃CT（Plan3D）were designed，respectively. The planning target volume（PTV），the V5，V20，V14.4， MLD of both ipsilateral lung and bilateral lung，the normal tissue complication probability（NTCP）of the bilateral lung，heart Dmax，esophagus Dmax，the NTCP of the esophagus，spinal cord Dmax and proximal bronchial tree Dmax were compared. Results Statistically significant differences were found between Planall and Plan3D for all dosimetric parameters except spinal cord Dmax（P < 0.05）. Compared with Planall，Planpro showed further reductions in PTV，ipsilat⁃ eral lung V5，V20，V14.4，MLD，bilateral lung V5，V20，V14.4，MLD，NTCP，heart Dmax and esophagus NTCP compared to Plan30⁃70 by 8.42 cc，2.06%，1.02%，26.67 cc，0.58 Gy，2.35%，0.63%，32.89 cc，0.43 Gy，0.1%，1.72 Gy and 0.09%（P = 0.004，< 0.010，0.006，< 0.001，0.006，0.004，< 0.001，0.010，< 0.001，0.005，< 0.001，0.026）. Conclusion In SBRT for early ⁃ stage NSCLC，conventional population margin ⁃based 3D ⁃CT plans overestimated PTV and increased the exposure dose to organs at risk；respiratory motion management technologies，especially pro⁃ spective gating，could better protect normal tissues and organs in the chest and reduce adverse effects of radiotherapy.

Key words:

non?small?cell lung cancer, respiratory?gated imaging techniques, stereotactic body radia? tion therapy, volumetric modulated arc therapy, flattening filter free