| Objective:Radiotherapy plays an important role in the comprehensive treatment of cervical cancer.In young patients with early-stage cervical cancer,long-term survival is possible after surgery combined with radiation therapy.Intraoperative preservation and translocation of the ovaries can maintain the endocrine function of the ovaries for a period of time after the treatment,which can delay the menopause and improve the quality of life of the patients.However,the function of ovaries may be damaged due to high dose of radiation during postoperative radiotherapy.Therefore,for young cervical cancer patients,it is particularly important to protect ovary and other vital organs during postoperative radiotherapy.This study was conducted to investigate the dosimetric differences in the target and organs at risk in young patients with cervical cancer undergoing postoperative radiotherapy under the treatment of fixed-jaw and jaw motion.The dosimetric verification of the two plans will provide data support and research reference for the selection of clinical treatment plan in the future.Methods:Thirty-six young cervical cancer patients who received IMRT after hysterectomy in the Gynecologic oncolo Gy department of our hospital were selected for postural fixation using body model.The pelvic cavity was scanned with CT of GE,and the scanning layer was 3mm thick.The scanned images were transmitted to Pinnacle9.2(Philips TPS),via an internal network system.Target and organs at risk were mapped by the same senior attending physician in conjunction with patient clinical imaging and examination data.Then the senior physicist designed the fixed-jaw plan and the jaw motion plan respectively under the same optimal conditions,and compared the dosimetric parameters of target and organs at risk under the two methods.The differences in MU and treatment time between the two programs were evaluated.The designed plan was transplanted to the verification module,and the mapcheck(two-dimensional dose verification system)was used for dose verification,and the differences between the two methods of treatment planned dose verification were compared.Result:1.The conformal index and homogeneity index of FJ plan and JM plan were0.81±0.05,0.77±0.08,0.10±0.03 and 0.14±0.05,respectively,and the P values of both of them were 0.001,showing a significant difference.Meanwhile,V100(%)of PTV dose coverage in target were 95.66±1.04 and 94.55±1.52,respectively.P is0.001.The approximate maximum dose of D2 was(4860.56±34.19)cGy and(4924.33±14.20)cGy,and the approximate minimum dose was(4376.00±108.12)cGy and(4257.33±211.76)cGy,respectively.They all have a P value of 0.001.2.In FJ plan and JM plan,the maximum dose of left ovary was(369.78±106.87)cGy and(446.59±72.49)cGy,respectively,and the P value was 0.001.The maximum dose of the right ovary was(375.33±111.50)cGy and(453.26±77.88)cGy,respectively,and the P value was also 0.001,showing a significant difference.The mean dose of ovary was(244.72±73.19)cGy,(324.53±76.35)cGy,(249.28±79.90)cGy and(331.20±82.41)cGy,respectively.3.There were significant differences in mean and maximum doses of bladder and rectum between FJ plan and JM plan.Bladder V45 was(20.22±6.34)% and(20.95±6.78)%,respectively.Rectal V45 was(28.10±15.92)% and(31.00±14.60)%,respectively.P value was 0.002,and there were statistically significant differences(P < 0.05).4.There were significant differences in total MU and treatment time between FJ plan and JM plan.The total MU was(657.33±43.05)MU and(786.56±82.54)MU,respectively.P value is 0.001;The treatment time was(377.78±14.84)s and(442.56±29.27)s,respectively.The total MU and treatment time in JM plan were higher than those in FJ plan,and the difference was statistically significant(P < 0.05).5.The dosimetric verification indexes of 3% / 3mm were(97.22±0.48)% and(96.24±1.40)%,respectively.P was 0.051,showing no statistical difference.Conclusion:This study compared the dosimetric differences of FJ and JM in postoperative radiotherapy for young cervical cancer patients,and explored a more reasonable radiotherapy planning method to reduce the dose to organs at risk and protect normal tissues.There was a significant difference in ovarian dose between the two plans.The fixed-jaw plan had lower ovarian dose and lower average dose than the jaw motion plan,and the comparison results were statistically significant(P < 0.05).There were significant differences between FJ plan and JM plan in rectal,bladder and femoral head volume indexes,but no significant differences in spinal cord maximum dose.There was no significant difference in the dosimetric verification index of 3%/3mm.Both plans meet clinical requirements,but FJ has more dosimetric advantages.The application of fixed-jaw technolo Gy to protect the organs at risk in postoperative radiotherapy for young cervical cancer patients is conducive to the better protection of important tissues and the improvement of the quality of life in the later period.The total MU and treatment time in the jaw motion plan were higher than those in the fixed-jaw plan,and the difference was statistically significant(P < 0.05).It can be seen that fixed-jaw can reduce the treatment time of patients and improve machine efficiency. |
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