| Purpose: In the afterloading treatment of cervical cancer,with the help of dosimetric and radiobiological models,the comparative analysis of various parameters in the treatment plan system aims to provide a basis for the selection of optimization methods for intracavitary/interstitial brachytherapy(IC/ISBT)in clinical treatment of cervical cancer.Methods:1.A total of 65 cervical cancer patients who received image-guided IC/ISBT in the brachytherapy Center of Sichuan Cancer Hospital from August 2021 to September 2022 were selected.The brachytherapy treatment plans were optimized using Graphical Optimization(GO),Inverse Planning Simulated Annealing(IPSA)and Hybrid Inverse Planning Optimization(HIPO),prescription dose high risk clinical target volume(HRCTV)D90% = 6 Gy.To evaluate the performance of the different plans,the following statistics were calculated: the time and isodose line,D100,V150%,V200% of HRCTV,homogeneity index(HI)and conformality index(CI),D1 cc and D2 cc for organs at risk(OAR)(bladder,rectum,intestines),biologically effective dose(BED),equivalent and uniform biologically effective dose(EUBED),tumor control probability(TCP),normal tissue complication probability(NTCP).The non-parametric Friedman test and non-parametric Wilcoxon rank test were used to analyze the time,dosimetric and radiobiological differences of the three optimization plans for the dose-volume parameters of different treatment schemes.2.A total of 32 cervical cancer patients who received image-guided IC/ISBT in the brachytherapy Center of Sichuan Cancer Hospital from August 2021 to September 2022 were selected.The brachytherapy treatment plans were optimized using IPSA;HIPO1,with a locked uterine tube;and HIPO2,with an unlocked uterine tube.We analyzed the dosimetric and radiobiological differences of the three optimization plans for the dose-volume parameters using the matched-samples t-test and Friedman test.Results:1.IPSA and HIPO took less time than GO,the time was GO(135.03s),IPSA(46.53s)and HIPO(98.36s).In the target dose,the V150%(53.66%)of the high-dose irradiation in HIPO was slightly higher than in GO(53.49%)and IPSA(52.28%),while the V200%(30.29%)of the high-dose irradiation was higher in GO than in IPSA(28.09%)and HIPO(29.36%),the CI of GO(0.91)was better than in IPSA(0.80)and HIPO(0.82),and the difference was statistically significant.In the OARs doses,the doses of the D1cc(4.58 Gy)and D2cc(4.35 Gy)to the bladder and the D1cc(4.10 Gy)and D2cc(3.75 Gy)to rectum were the lowest in HIPO,and there was no significant difference in the intestinal dose.In the comparison of radiobiological dose,the HIPO EUBED of D90(12.35 Gy)was higher than in GO(12.23 Gy)and IPSA(12.13 Gy),the EUBED GO(2.38 Gy)and HIPO(2.39 Gy)of the bladder dose were lower than in IPSA(2.42 Gy),and the EUBED of rectal irradiation was the lowest in HIPO(3.74 Gy).There was no significant difference in intestinal EUBED.There was no significant difference in the TCPs predicted by the three plans(p=0.055),and HIPO(0.16%,0.95%)predicts that the NTCP of the bladder and rectum was lower than that of GO(0.18%,1.62%)and IPSA(0.17%,1.36%),and the NTCP of the intestine did not show significant difference.2.Compared with IPSA and HIPO2,HIPO1 had better V150%(55.33±2.81%)and V200%(34.27±2.81%)(p<0.05).Compared with IPSA(3.00±0.45 Gy,0.79±0.06)and HIPO1(3.25±0.31 Gy,0.80±0.07),HIPO2(3.28±0.37 Gy,0.82±0.07)had better D100 and CI(p<0.05).The doses to the bladder D1cc(4.72±0.33 Gy)/D2cc(4.47±0.29 Gy)and rectum D1cc(4.50±0.61 Gy)/D2cc(4.11±0.63 Gy)were lower in HIPO2 than in IPSA and HIPO1,the difference was statistically significant.The mean doses of the intestines were similar(P>0.05).The EUBEDs for D90 were higher in HIPO1(12.32±0.18Gy)and HIPO2(12.33±0.24 Gy)than in IPSA(12.13±0.30 Gy)by 1.57%and 1.65%,respectively.However,the TCPs were not remarkably different among the three plans(p>0.05).Also,the NTCP for the bladder was lower in HIPO2(0.20%)than in IPSA(0.23%)and HIPO1(0.24%)by 13.04% and16.67%,respectively.Conclusion:1.Among the optimization methods studied,inverse optimization takes less time than GO,and GO is more conformable than IPSA and HIPO;HIPO can increase the biological coverage dose of the target area,reduce the maximum dose of the bladder and rectum in both physical and biological aspects,and also reduce the NTCP of the bladder and rectum.HIPO is recommended as an optimization algorithm in IC/ISBT of cervical cancer.2.The dosimetric parameters of IPSA,HIPO1 and HIPO2 are comparable.HIPO2 provides better dose conformability and lower NTCP.HIPO2(with an unlocked uterine tube)is recommended as an optimization algorithm in IC/ISBT of cervical cancer. |
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