Abstract: Objective To evaluate and compare the dosimetry achieved using three-dimensional conformal radiotherapy（CT-3DCRT） with that achieved using cone-beam computer tomography adaptive radiotherapy（CBCT-ART） in patients with non-small cell lung cancer，in order to provide a basis for selecting the best clinical treatment strategy.Methods Ten patients with non-small cell lung cancer were treated in our hospital between June 2010 and October 2011，first using hypofractionated CT-3DCRT，with CBCT verifi-cation performed before each fraction，and then using CBCT-ART. Dosimetry of target and normal tissue was compared between the two CT approaches using dose-volume histograms.Results In the CBCT-ART approach，V20 of the affected side of the lung was（9.5±3.45）% and the Dmax of the spinal cord was （25±12.7） Gy，while the corresponding values in the CT-3DCRT approach were（11.5±3.5）% and（27±13.2） Gy（P<0.05）. Adaptive radiotherapy can significantly reduce the radiation exposure of normal tissue compared with three-dimensional conformal radiotherapy.Conclusion Using target volume changes in each CBCT image to adjust the dosing regime can significantly reduce the radiation exposure of adjacent normal tissue，which may allow use of a higher target dose and sub-sequent improvement in local control.

Key words: Conebeam CT, Adaptive radiotherapy, Three-dimensional conformal radiotherapy