Clinical Observation Of Intracavity Combined With Interstitial Brachytherapy For Cervical Cancer And The Dosimetric Comparison Of Three Different Brachytherapy Methods

Objective:To review the short-term efficacy and radiation toxicity of intracavitary combined with interstitial brachytherapy in the radiotherapy center of our hospital;To compare the dosimetric differences of intracavitary combined with interstitial brachytherapy,intracavitary brachytherapy and interstitial brachytherapy in target volume and endangered organs;and to determine whether intracavitary brachytherapy combined with brachytherapy has dosimetric advantages.To explore the maximum treatment boundary of cervical tumor by using simple intracavitary technique based on the dose limit of endangering organs,so as to provide guidance for future clinical work.Materials and methods:A total of 14 patients with cervical cancer who received 192Ir high dose rate intracavitary combined with interstitial brachytherapy(IC/ISBT)in our center from April 2019 to June 2020 were enrolled for short-term clinical efficacy and radiotherapy toxicity analysis.Select the actual IC/ISBT radiotherapy plan completed by our center,copy the image,and simulate the simple ISBT and ICBT plan under the condition that the sketches of HR-CTV,IR-CTV,bladder,rectum and sigmoid colon were consistent.All brachytherapy plans were based on the same target dose requirements:prescription dose IR-CTV D90 is 600cGy,bladder D0.1cc<500cGy,rectum and sigmoid D2cc<420cGy.All three groups of plans used mixed reverse therapy plan to optimize(HIPO)and manually adjusted to meet the OAR dose limit as the standard,so that the target area can get the highest possible dose.Evaluate the target dose parameters of HR-CTV:D90,D98,D100,V100,V150,V180,V200.IR-CTV target dose parameters:D90,V100,V150,V180,V200.Endangered organs collected D0.1cc and D2cc datas.Fourteen patients completed a total of 23 IC/ISBT plans,copied images and completed 23 simulated ICBT plans.Copying IC/ISBT image to make simulated ISBT plan,under the condition of reaching the above dosimetric limit,IR-CTV D90≥90%prescription dose is required,and there are 11 ISBT plans up to the standard,which are compared with the corresponding IC/ISBT.Twenty-three plans of different patients who have completed only intracavitary brachytherapy in our center were selected,and 23 plans were remade.When the dose of bladder,rectum or sigmoid colon reached the limited dose,the distance from the isodose line of 600cGy in the cross section of 2cm at the fornix of vagina to the central axis of uterine cavity was measured.Statistical analysis of relevant data.Results:1.Clinical effect observation:the total effective rate of 14 patients was 100%;radiation toxicity after 3 months follow-up:8 cases had radiation cystitis(51.7%),all were grade 1 radiation cystitis;5 cases had radiation proctitis(35.7%),all were grade 1 or grade 2 radiation proctitis;5 cases had radiation vaginitis(35.7%),all were grade 1 radiation vaginitis.2.Dosimetry comparison:compared with ISBT,IC/ISBT had obvious advantages in the doses of HR-CTV D90,V100(P=0.016、0.013).Compared with ICBT,IC/ISBT had dosimetric advantages for HR-CTV D90,D98,D100,V100,V150,V180,V200(P=0.002,0.001,0.017,0.007,0.002,0.003,0.004)and CTV D90,V100(P=0.022,0.045).There was no significant difference in D0.1cc and D2cc between IC/ISBT and ISBT or ICBT in bladder,rectum and sigmoid colon.3.In 23 actually completed cases of ICBT plan,measure the distance between the cross-sectional 600cGy isodose line of 2cm on the fornix of vagina and the central axis of uterine canal,the median was 30.86mm,with an average of 30.1 mm,range:26.4mm-40.9mm.Conclusion:1.In this study,IC/ISBT has a good total effective rate and acceptable radiation toxicity in the treatment of cervical cancer.2.Compared with ICBT or ISBT,IC/ISBT has obvious advantages in target dose,and does not increase the dose of endangering organs.3.When the boundary of the tumor is far from the central axis of the uterine canal,and the boundary of the cross section of 2cm on the fornix of vagina(Point A level)is more than about 3cm from the central axis of the uterine canal,ICBT can not achieve the limited dose of the endangered organ and get ideal dose of the target volume,so the implantation needles are needed this time.