| [Object]①To investigate the dosimetric characteristics of Helical Tomotherapy(HT),step-and-shoot intensity-modulated radiation therapy (SaS-IMRT) and three-dimensional conformal radiation therapy(3D-CRT) during the treatment of prostate cancer as well as their comparison in protecting the organs at risk(OAR).②To evaluate the early and late side effects in prostate cancer patients treated with HT.[Methods]①The CT images of 17 HT-treated patients with localized prostate cancer were transferred into HT,SaS-IMRT and 3D-CRT planning system,respectively,after the target region and organs at risk were drawn out.Each prescribed dose for three kinds of plans was 76Gy/35 fractions. The limit doses of organs at risk:rectum V70<25%,V65<35%,V60<5O% ,V40<45%,and the average dose<55Gy;bladder V70<35%,V65<50%,the average dose<60Gy;femoral head V40<40%,the maximum dose <50Gy. Datas of the three systems were analyzed by t test.②The early and late side effects of gastrointestinal and genitourinary were evaluated among 12 patients using RTOG grading criteria and RTOG/EORTC grading criteria, respectively.[Result]①Each of the three plans showed ideal distributions for the prescribed target dose through dosimetric comparison.The conformity index(CI)in HT,SaS-IMRT and 3D-CRT were 0.835±0.028,0.741±.025 and 0.619±0.023,respectively,which appeared intergroup significant differences(P<0.05).The homogeneity index(HI)was 1.070±0.013,1.083±0.017 and 1.068±0.018,The value of HI in HT was less than that of SaS-IMRT(7><0.05).②Dose comparison of calulated OAR:within three groups of plans(HT/SaS-IMRT/3D-CRT),the average dose,V20,V30,V40,V50, V60 and V65 of rectum(P<0.05 or P<0.01) in HT were lower than those in two other groups,except V10.And the average dose,V30,V40,V50,V60,V65 and V70(except V10 and V20) of bladder(P<0.05 or P<0.01) showed the same trend.V40,V50,V60,V65 and V70 of rectum in SaS-IMRT were lower than those in 3D-CRT(P<0.05).In addition,the average doses,the maximum dose, V20,V30 and V40 of femoral heads(P<0.05) in HT group displayed better than those in the other groups,③Acute and chronic effects of OAR in HT: Grade 0,1 and grade2 acute gastrointestinal toxicities were observed in 17%,50%and 33%.Grade 0,1,2 and 3 acute genitourinary toxicities were accounted for 33%,59%,0%and 8%,respectively.Grade 1,2 and Grade 3 chronic gastrointestinal toxicities were observed in 67%,25%and 8%.Grade 0 and Grade 1 chronic genitourinary toxicities were accounted for 92%and 8%. [Conclusion]①Comparing with SaS-IMRT and 3D-CRT,HT technique in treating prostate cancer had better conformity and steeper dose gradient,as well as organs at risk sparing.The homogeneity index(HI) and savage for organs at risk in IMRT were better than those in 3D-CRT.②Grade 3 acute and late gastrointestinal toxicities above were not observed among the patients treated with HT during follow-up period,as well as Grade 3 acute and late genitourinary toxicities. |
