Investigating The Impact Of Prostate Cancer Radiotherapy On The Biological Behavior And Specific Mortality Of Subsequent Bladder Cancer Using Big Data

Background Localized prostate cancer is caught early with the spread of prostate cancer screening with prostate specific antigen.Radiotherapy,as one of the standard treatments for localized prostate cancer,has been used more and more in clinical practice.The attention on side effects of radiotherapy are increasing.One of the most serious side effects is radiotherapy related second primary cancer.The bladder is an organ adjacent to the prostate.Radiotherapy for prostate adenocarcinoma may have an effect on the incidence of bladder cancer.Previous studies have partially explored the impact of prostate cancer radiotherapy on the incidence of bladder cancer.However,it is still unclear whether the effects of different types of prostate cancer radiotherapy on the incidence of second bladder cancer,tumor characteristics,and mortality are all different.In addition,due to the low overall incidence of second bladder cancer after prostate cancer,small sample studies did not provide sufficient statistical power,and the emergence of big data facilitated the study of such kind bladder cancer.Objective This study aimed to use big data to study the effects of different treatments for prostate cancer on the incidence,tumor biological characteristics,and tumor-specific death of second primary bladder cancer.Material and methods A total of 530581 patients in the Surveillance,Epidemiology,and End Results database with localized PCa between 1988 and 2013 were identified.PCa treatments included radical prostatectomy(RP),external beam radiotherapy(EBRT),radioactive implants(RI),and combined EBRT and RI(EBRI).A multivariable competing risk analysis based on a proportional sub distribution hazards model was used to determine the impact of different radiotherapy modalities on BCa incidence and specific mortality.Results Incidence of BCa was significantly high in patients treated with EBRT,RI,and EBRI versus RP(Sub distribution hazard ratio[SHR]:1.41,P<0.001;SHR:1.58,P<0.001;SHR:1.56,P<0.001 respectively).BCa following EBRT,RI,and EBRI were more commonly non-urothelial(3.3%,2.9%,3.3%,respectively,versus 1.2%)and T4(3.5%,6.1%,5.0%,respectively,versus 1.6%)compared with RP.RI associated with a higher rate of BCa metastasis than RP(2.6%vs.1.1%).Prior EBRT,RI,and EBRI increased BCa-SM(SHR=1.44,P=0.001;SHR=1.21,P=0.047;and SHR=1.42,P=0.032 respectively).Conclusions Patients receiving radiotherapy for PCa have a higher risk of BCa.BCa after EBRT,RI,and EBRI is more likely to be non-urothelial,stage T4,and with increased BCa-SM.Prior RI associated with a higher rate of BCa metastasis.