| Purpose:This study performed a dosimetry comparison of three-dimensional conformal radiotherapy(3D-CRT),seven-field intensity modulated radiation therapy(7F-IMRT)and Volumetric-modulated Arc Therapy(VMAT)in postoperative endometrial cancer patients.The purpose of this study was to find the best external radiotherapy technique of these patients.Materials and methods:20 patients with FIGO staging as stage II-IIIC1 endometrial cancer at Jiangxi Cancer Hospital from September 2018 to September 2020 were conducted.Under the strict direction of preplan,3D-CRT,7F-IMRT,and VMAT plans were designed on pinncle treament planning system with 6MV photon beams.Prescribed dose was50Gy/25 fractions with goal coverage of 95% PTV by 100% of the prescription.The same dosage constraint conditions were used in 7F-IMRT and VMAT plans.The three types of plans were compared in terms of conformity index(CI)and homogeneity index(HI),organ at risk(OAR)sparing and the number of monitor units(MU).Results:3D-CRT,7F-IMRT and VMAT treatment plans met the target area prescription dose requirements.The conformity index and homogeneity index of VMAT were better than 7F-IMRT and 3D-CRT.The CI values in the VMAT,7F-IMRT and3D-CRT were 0.89±0.42,0.85±0.44,0.64±0.03 respectively,and the HI values were1.05±0.01,1.07±0.01,1.08±0.01 respectively,and the differences among the three plans were statistically different(P<0.05).With regard to average dose to organs at risk,especially in the pelvic bone marrow,VMAT was lowest with 3294.00 c Gy,which was lower than 7F-IMRT(3294.00 c Gy)and 3D-CRT(3356.61 c Gy),and the difference was statistically significant(P<0.05).With regard to the bowel bag,left/right femoral heads,rectum,and bladder,the average doses of VMAT and7F-IMRT were lower than 3D-CRT,and the difference was statistically significant(P<0.05).Compared with 7F-IMRT,the average doses of bladder and left femoral head were slightly higher(4367.28 c Gy VS 4304.85 c Gy,2151.03 c Gy VS 2038.20 c Gy)than VMAT.There was no statistically significant difference.In terms of the volume of organ-at-risk involvement,VMAT(73.42±4.33%)had lower dose involvement volume than 7F-IMRT(75.65±3.14%)and 3D-CRT(86.10±5.56%)in the V20 parameters of pelvic bone marrow.compared with 3D-CRT,V30,V40,and V50 of pelvic bone marrow,bowel,bladder,and rectum were all reduced in both VMAT and7F-IMRT plans.Furthermore,VMAT is slightly better than 7F-IMRT.In the7F-IMRT plans,V30,V40 of left/right femoral heads were lower than VMAT.However the difference between the two plans were not statistically significant(P>0.05).For distribution volumes of low doses such as V5 and V10,3DCRT in the pelvic bone marrow,bowel bag were lower than 7F-IMRT and VMAT.V5 and V10 of the pelvic bone marrow in 3D-CRT plans were lower than 7F-IMRT and VMAT.And the difference were statistically significant(P<0.05).And the 7F-IMRT is slightly lower than VMAT,however there is no statistical difference between them(P>0.05).In terms of monitor units,the monitor units of the 3D-CRT was the least.The monitor units of VMAT,7F-IMRT and 3D-CRT were 666.50±102.48,716.65±102.17,287.10±6.74,respectively.Conclusion:1.In terms of the conformal dgree and dose uniformity of the target volume,VMAT plan was better than 3D-CRT and 7F-IMRT.2.In terms of pelvic bone marrow protection: VMAT had better dosimetry advantages in V20,V30,V40,and V50.However,in low-dose areas,the V5 and V10 were increased.3.In terms of protection of other organs at risk,V30,V40,and V50 in the high-dose areas of the bowel bag,bladder,and rectum in IMRT plans were reduced.4.In terms of pure treatment time: 3D-CRT has certain advantages.5.VMAT technology was recommend as the first choice of the treament for postoperative endometrial cancer patients who need external radiation therapy,followed by 7F-IMRT.However,due to the unavailable equipments and economic reasons,3D-CRT was also suitable for the patients who can not afford VMAT or IMRT. |
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