Abstract
BackgroundThe purpose of this study is to evaluate the dosimetric benefits of a proton arc technique for treating tumors of the para-aortic lymph nodes (PALN).MethodIn nine patients, a proton arc therapy (PAT) technique was compared with intensity modulated radiation therapy (IMRT) and proton beam therapy (PBT) techniques with respect to the planning target volume (PTV) and organs at risk (OAR). PTV coverage, conformity index (CI), homogeneity index (HI) and OAR doses were compared. Organ-specific radiation induced cancer risks were estimated by applying organ equivalent dose (OED) and normal tissue complication probability (NTCP).ResultsThe PAT techniques showed better PTV coverage than IMRT and PBT plans. The CI obtained with PAT was 1.19 ± 0.02, which was significantly better than that for the IMRT techniques. The HI was lowest for the PAT plan and highest for IMRT. The dose to the OARs was always below the acceptable limits and comparable for all three techniques. OED results calculated based on a plateau dose–response model showed that the risk of secondary cancers in organs was much higher when IMRT or PBT were employed than when PAT was used. NTCPs of PAT to the stomach (0.29 %), small bowel (0.69 %) and liver (0.38 %) were substantially lower than those of IMRT and PBT.ConclusionThis study demonstrates that there is a potential role for PAT as a commercialized instrument in the future to proton therapy.
Highlights
organ equivalent dose (OED) results calculated based on a plateau dose–response model showed that the risk of secondary cancers in organs was much higher when intensity-modulated radiation therapy (IMRT) or proton beam therapy (PBT) were employed than when proton arc therapy (PAT) was used
This study demonstrates that there is a potential role for PAT as a commercialized instrument in the future to proton therapy
New technologies in the delivery of radiation therapy have included the use of intensity-modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) with linear accelerators, as well as the development of proton beam therapy (PBT), which has increased the ability to maximize the dose to the tumor while sparing normal structures
Summary
New technologies in the delivery of radiation therapy have included the use of intensity-modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) with linear accelerators, as well as the development of proton beam therapy (PBT), which has increased the ability to maximize the dose to the tumor while sparing normal structures. [1,2,3] This is because of the advantageous physical properties of protons, including a near zero exit or distal dose just beyond the target volume, resulting in reduced proton doses to normal tissue, with better conformation of the dose to the target volume. These unique dose characteristics of protons may reduce the risk of acute as well as late side effects [4]. This study used proton arc plans with 16 spaced, static, passively-scattered proton beams They reported that the predicted risk of cancer for an outof-field organ such as the bladder or rectum following proton arc therapy is either less than or approximately equal to the risk with VMAT. The purpose of this study is to evaluate the dosimetric benefits of a proton arc technique for treating tumors of the para-aortic lymph nodes (PALN)
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