Application Of Injection Based Bladder Filling In Postoperative Radiotherapy For Cervical Cancer

Postoperative radiotherapy is one of the main ways of comprehensive treatment for cervical cancer.However,due to the large displacement of the organs near the target area,the conventional localization method is likely to cause irradiation errors.How to ensure the accuracy of postoperative radiotherapy for cervical cancer has become a research focus.At present,the most effective way to improve the accuracy of postoperative radiotherapy for cervical cancer is urinary bladder filling.It pushes the organs at risk such as small intestine and rectum outside the target area as far as possible,which will further reduce the adverse reactions of surrounding organs and improve the quality of life of patients on the basis of effective treatment.At present,the common clinical bladder filling method is spontaneously holding back urine,which depends on patients’ subjective feelings and is difficult to accurately control the repeatability.In recent years,the precise control of bladder filling by reverse injection of quantitative normal saline is valued in clinical practice.This method can accurately control bladder filling and is relatively objective.In this study,the set-up errors of radiation fields and the dosimetric difference caused by the two filling methods in postoperative radiotherapy for cervical cancer were analyzed.The differences in adverse reactions between the two groups of patients were further discussed,in order to provide a theoretical basis for the future clinical selection of bladder filling methods.According to the preset inclusion and exclusion criteria,50 cervical cancer patients with postoperative radiotherapy admitted to the Department of Radiotherapy of the First Affiliated Hospital of Sun Yat-Sen University from June 2018 to June 2019 were selected.The patients were randomly divided into 2 groups(injection based bladder filling group and spontaneous urine holding control group)of 25 patients each.CT localization and target volume delineation were performed in these two groups 1 hour after quantitative injection of normal saline and spontaneously holding back urine,respectively.The PTV was implemented by IMRT,expanding outward by 7～15mm in all directions on the basis of CTV.The prescriptions and fractionated dose were 50Gy/2Gy/25f.Collecting the first and last image data of these two groups by CBCT in the linear accelerator,the set-up errors of left-to-right,headto-foot,and abdominal-to-dorsal directions were obtained.The maximum target dose,minimum target dose,mean target dose,target volume coverage,conformation index and homogeneity index of these two groups were calculated by the planning system.The subjective and objective indicators such as early adverse reactions,acceptance and hematological changes were analyzed by the progress notes,questionnaire survey and CBC.The set-up errors in the abdominal-to-dorsal direction of the injection based bladder filling group and spontaneous urine holding control group were(1.8 5±1.14)mm and(2.81±2.17)mm,respectively,and the differences were significant(P<0.05).However,there was no significant difference in the left-to-right direction and the head-to-foot direction(P>0.05),The mean target doses,target volume coverage,conformation indexes and the homogeneity indexes of the target area of these two groups were(5171.1±24.1)cGy and(5131.7± 128.6)cGy,(94.51±2.8)%and(92.7±4.0)%,0.70±0.05 and 0.68±0.07,1.07±0.02 and 1.08±0.02,respectively.All the results in the injection based bladder filling group were significantly better than the spontaneous bladder control group(P<0.05).The incidence of early genitourinary adverse reactions in the injection based bladder filling group was 36%lower than the spontaneous bladder control group(P<0.05),while the platelet count and hemoglobin were significantly higher(P<0.05).Furthermore,the injection based bladder filling method was acceptable in 92%of patients in the injection based bladder filling group.In summary,injection based bladder filling can reduce the set-up errors of target location,improve the accuracy and the conformity of the target dose,and reduce the occurrence of adverse reactions.Patients have a higher acceptance to this method.Therefore,it is recommended to use injection based bladder filling method for postoperative radiotherapy of cervical cancer patients.