Effect Of Source Activity On Efficacy And Adverse Events Of Locally Advanced Cervical Cancer Patients In Brachytherapy

Objective:I aimed to explore the effect of radiation source activity on the short-term and long-term efficacy and adverse events of patients with locally advanced cervical cancer who received ¹⁹²Ir brachytherapy.Methods:Thirty-six patients with locally advanced cervical cancer who received brachytherapy in the second affiliated hospital of Jilin University from November 2017 to April 2018 were included.The eligible patients were divided into low activity group and high activity group according to the radiation source activity of brachytherapy.The baseline characteristics of the two groups were collected,and the tumor size on MRI images at the beginning of brachytherapy and one month after brachytherapy were measured.The volume change and the volume change rate were calculated,and the objective response rate and complete response rate were evaluated.The two groups were followed up for 3 years,and progression free survival,overall survival and radiation-related adverse events between the two groups were compared and analyzed.Results:1.The patients were divided into low activity group（0.73-1.45 Ci）and high activity group（4.26-8.95 Ci）according to the activity of radiation source and there were 18 patients in each group.There were no significant differences in ages,FIGO stages,pathological characteristics,external radiation dose and fractionation,pelvic lymph node dose,tumor volume before brachytherapy,internal radiation dose and fractionation,the number of needles in patients with interstitial implantation and the value of SCC before treatment.2.There were no significant differences between the two groups in the volume percentage of prescription dose,HR-CTV V100 and HR-CTV D90in a single brachytherapy procedure.3.There were no significant differences in tumor volume change,volume change rate and objective response rate between the two groups.However,the 1-month complete response rate in high activity group（44.4%）was significantly higher than that in low activity group（5.6%）,P=0.018.4.There was no significant difference in three-year OS and PFS between high and low activity groups.5.The incidence of radiation proctitis in high activity group（50%）was significantly higher than that in low activity group（11.1%）,P=0.027.Conclusions:1.The activity of brachytherapy source（4.26-8.95 Ci vs.0.73-1.45Ci）will have an influence on the complete response rate of patients with locally advanced cervical cancer;when the activity of brachytherapy source is high,the complete response rate of patients in one month is higher.No effect of radiation source activity on one-month objective remission rate,tumor volume change rate of patients with locally advanced cervical cancer was observed.2.The activity of brachytherapy source has no effect on the progression free survival and overall survival of patients.3.High activity of brachytherapy source will increase the incidence of radiation proctitis.