Effect Of Bladder Volumes On Normal Tissue Doses In Interstitial Brachytherapy For Locally Advanced Cervical Cancer

Objective:To evaluate the effect of bladder volumes on normal tissue doses in interstitial brachytherapy for locally advanced cervical cancer patients.Methods: The study included 25 patients with stage Ib2-Ⅲb advanced cervical cancer who were admitted to our department from April 2015 to July 2015 and received radical external beam radiotherapy and interstitial brachytherapy.Filling the bladder respectively with 0、50、100、150ml liquid during interstitial brachytherapy,delineating target volume and OAR(organs at risk) under different bladder filling status by the same doctor,developing treatment plans at different bladder filling status,evaluating the doses(D2cc、 D1cc、 D0.1cc, respectively)for the bladder,rectum,sigmoid colon according to DVH and analyzed by paired t-test.Results:The bladder D2 cc with bladder volume of 50 were significantly reduced compared with those(0、100、150ml) bladder filling status(P=0.03、0.037、0.001);The bladder D1 cc with bladder volume of 50 were significantly reduced compared with those(0、150ml) bladder filling status(P=0.07、0.002);The bladder D0.1cc with bladder volume of 50 were significantly reduced compared with bladder filling with 150ml(P=0.020).Conclusions:The doses to the bladder are influenced by different bladder filling status.but the doses to the sigmoid colon and rectum show no significant variation.Without any change in the prescribed dose,the bladder volume of 50 is more beneficial to reduce the dose to the bladder than those(0、100、150ml) bladder filling status.