Bladder absorbed dose in intracavitary brachytherapy to cervix cancer by using orthogonal radiographs: late effects, posterior bladder wall dose and p53, ATM and Mdm2 polymorphisms

Abstract

The urinary bladder is one of the organs at risk affected by irradiation of patients with cancer of the uterine cervix, especially during brachytherapy. The dose delivered to the bladder during brachytherapy is calculated in only one reference point, as recommended by the ICRU 38 that underestimates the maximum dose delivered to the bladder posterior wall. Computed tomography and magnetic resonance image-based brachytherapy are being studied, in order to better define the dose/volume relationship for the organs at risk. However, these more sophisticated exams are not worldwide available, mainly for developing countries, where uterine cervix cancer is most prevalent. The purpose of this study is to validate a model for calculation of the bladder dose during brachytherapy, already developed by the authors. A group of fifty patients submitted to radiotherapy for cancer of the uterine cervix, with at least 6 months follow-up will be studied. Late effects on bladder will be analyzed by cystoscopy. Also, individual genetic factors related to a higher radiosensitivity will be studied by the association of p53, ATM and MDM2 polymorphisms with the late effects. (AU)