Abstract: Objective The Objectives of this study were to investigate the advantages and disadvantages of three external radiation radiotherapy regimens in the treatment of advanced cervical cancer,and to compare dosimetry of the planning target volume(PTV)with various crisis organs.Methods A total of 90 patients with cervical cancer(stage II B or above)who were treated in our hospital from September 2015 to October 2019 were randomly divided into three ABC groups(30 patients/group).The radiotherapy plans of three-dimensional conformal radiotherapy(3D-CRT),the fixed field static intensity modulated radiotherapy(IMRT)and volume rotation intensity modulated radiotherapy(VMAT)were compared in the dosimetry.The advantages and disadvantages of three types of cervical cancer radiotherapy were discussed in combination with three-dimensional after loading equivalent biological doses.Results In terms of external irradiation target area,the average dose of PTV,conformity index CI and uniformity index HI of planned targets in overall three groups were statistically different(P＜0.05).The average dose,index HI and conformity index CI in the group A were significantly lower than those in the other two groups(P＜0.05).In terms of crisis organs by external exposure,the bladder,colorectal and small intestine of three plans of ABC were significant different(P＜0.05).Further comparison showed that the average dose of small intestine in the group A was higher over 13.7% than that in the group B,and higher over 28% than that in the group C(P＜0.05).The average dose of bladder was lower less 19.8% and 15.2% lower than that in the group B and C,respectively(P＜0.05).The average dose of colorectal was lower less 26.1% and 19.4% than that in the group B and C,respectively(P＜0.05).The average dose of small intestine in the group B was similar with the group C,there was no statistical difference(P＞0.05).The average doses of bladder and colorectal in the group B were higher over 5.7% and 9.1% than those in the group C,respectively(P＜0.05).The treatment time of group A was(135.5±27.6)s.the treatment time of group B was 7.6 times than that of group A and 4.8 times than that of group C.The target dose and organ-endangered dose of external irradiation combined with intracavitary irradiation in the three groups of ABC could meet the clinical requirements.Conclusion Volume-modulated intensity-modulated radiotherapy for patients with intermediate and advanced cervical cancer has certain advantages over other two schemes in terms of dose conformation at the target area and protection of endangered organs.“Half-field”conformal radiotherapy combined with three-dimensional brachytherapy at the target area also meets the clinical requirements."Half-field" three-dimensional conformal radiotherapy has the advantages of short treatment time and high plan execution efficiency.It has a significant price advantage compared with IMRT and is worthy of clinical promotion.

Key words: Cervical cancer, Three-dimensional conformal, Static field intensity modulation in fixed field, Volume rotation intensity modulation