A Domestric Comparison Of Intensity-modulated Radiotherapy,double Scattering Proton Beam Therapy And Intensity-modulated Proton Therapy For Paranasal Cavity Cancer

Purpose: We compared tumor and normal tissue dosimetry between Intensity-modulated Photon Radiotherapy(IMRT),Double Scattering Proton Beam Therapy(DS-PBT)and Intensity-modulated Proton therapy(IMPT)for paranasal cavity cancer.Methods Materials: To compare dosimetric differences between IMRT,DS-PBT and IMPT treatment for paranasal cavity cancer,Eight patients treated with Double Scattering Proton Therapy at University of Florida Proton Therapy Institute were collected and IMRT and IMPT plans were generated.To facilitate dosimetric comparisons,clinical target volumes and normal tissue volumes were held constant.Plans were optimized for target volume coverage and normal tissue sparing.Result: Target volume coverage was acceptable and comparable in IMRT,DS-PBT and IMPT plan,with at least 95% of the PTV2 receiving 95% of the prescribed dose in all cases.Compared with DS-PBT and IMRT,IMPT reduced the Max dose(D2)(p=0.08 DS-PBT,p=0.073 IMRT)and V107(p=0.037 IMRT,p=0.018 DS-PBT).Comfomal index of target was better for IMRT plan,and Homogenesis index was better for IMPT plan.The maximum dose for three plans to ipsilateral lens/opticnerve exceeded tolerated dose,and maximum dose for DS-PBT to ipsilateral retina exceeded tolerated dose.The maximum dose for three plans to contralateral lens exceededtolerated dose.The mean dose for IMRT,DS-PBT and IMPT to contralateral opticnerve were 39.00 Gy,19.13 CGE,38.20 CGE,DS-PBT was significantly better than IMRT plans(P = 0.003)and IMPT plan(P = 0.018),maximum dose for three plans to contralateral opticnerve were 53.25 Gy,CGE 36.21,and 54.72 CGE,DS-PBT was significantly lower than that IMRT and IMPT plan(P = 0.018 IMRT vs.DS-PBT,P = 0.003 DS-PBT vs.IMPT).The mean dose for IMRT,DS-PBT and IMPT to optic chiasma were 46.28 Gy,CGE 22.53 and 22.53 CGE respectively,DS-PBT were obviously better than IMRT plan(P = 0.001).V30 for DS-PBT plan to Ipsilateral parotid gland exceeded tolerated volume,but for IMRT and IMPT plans didn’t exceed.The mean dose for three plans to contralateral parotid gland didn’t exceed tolerated dose,they were 15.82 Gy,7.68 CGE,14.25 CGE respectivly.DS-PBT was significantly better than the IMRT plan(P = 0.008),and there was no statistical significance difference(P = 0.073)compared to IMPT plans,there was also no statistical significance(P = 1)difference between IMRT and IMPT plan.The mean dose of ipsilateral cochlea were as follows: 38.82 Gy,40.14 CGE,26.12 CGE,IMPT plan was significantly lower than that IMRT and DS-PBT(P value was 0.023),maximum dose of ipsilateral cochlea for the three are: 42.28 Gy,CGE 43.47 and 43.47 CGE,IMPT significantly lower than DS-PBT(P = 0.002),difference between IMRT and IMPT was not significant(P = 0.544).Mean dose for IMRT,DS-PBT and IMPT to the contralateral cochlea were: 30.23 Gy,5.45 CGE and 5.45 CGE,DS-PBT was significantly lower than IMRT plans(P < 0.001),when compared to IMPT there was no statistical difference(P = 0.184);the maximum dose for three plans were: 33.47 Gy,CGE 9.86 and 9.86 CGE,DS-PBT plan was also significantly lower than IMRT(P = 0.002),there was no significant statistical difference when it compared to IMPT plan(P = 0.544).When dose of iradicated nontargebody less than 20 Gy,DS-PBT and IMPT plans were significantly better than IMRT plan,when dose of iradicated nontargetbody was 20 Gy to 40 Gy,IMPT significantly reduced exposure volume compared to IMRT plan,and there was no significant difference between DS-PBT and IMRT plan.Conclution: All plans can substantially covered the target volume(s).IMPT can lower max dose and V107.Superior normal tissue dose distribution is achieved with proton radiation therapy(DS-PBT and IMPT)compared with IMRT.But all three therapy irradiated the ipsilateral optic structures and part of the contralateral optic structure beyond acceptable tolerance doses.