RÉSUMÉ
Objective To study the impacts of bladder filling status on the dosimetric parameters of the target volume and organs at risk (OAR) in intensity-modulated radiotherapy (IMRT) for prostate cancer.Methods Ten localized prostate cancer patients without serious complications treated with IMRT were selected for this study.These patients underwent CT scans of the whole pelvic cavity three times in different bladder filling status (empty and injected with 150 ml and 300 ml of normal saline) to obtain three series of pelvic CT images.The three sets of CT images were transferred to the treatment planning system.The target volume and OAR such as the rectum,bladder,and femoral heads were contoured by the same doctor.The treatment planning was performed and optimized by the physicist.The dosimetric parameters of the target volume and OAR in three bladder filling status were subjected to analysis by paired t-test.Results If the bladder filling status was consistent in orientation and radiation,the bladder filling status was not associated with the dosimetric parameters of the target volume and femoral heads (P =0.077-0.998 ; P =0.219-0.969) ;it had significant impacts on the dosimetric parameters of the bladder (P =0.000-0.562) and some dosimetric parameters of the rectum (P =0.000-0.645),and bladder filling was favorable for the protection of the bladder and rectum.If the bladder filling status was not consistent in orientation and actual radiation,the calculated planning target volume,the dosimetric parameters of the bladder,and some dosimetric parameters of the rectum were different from those in actual treatment (P =0.000-0.913).Conclusions For the prostate cancer patients treated with IMRT,it is recommended to keep the bladder well and consistently filled.