Rectal and bladder radiation dose during curative radiotherapy for cervix cancer at Universitas Hospital Oncology.
Introduction and aim. Cervical carcinoma is a huge burden on the South African population and health care system. Treatment of this disease has improved dramatically with the advent of 3D imaging capabilities combined with brachytherapy to deliver dose to the tumor and limit dose to organs at risk specifically the bladder and rectum. Recent guidelines give recommendations for dose limitations of these organs at risk, specific for a volume of 0.1cc, 1cc and 2cc. Our departmental dose prescription method for brachytherapy is unique by dose limitation to the rectum for each brachytherapy. The aim of this study was to determine the total dose of combined external beam radiotherapy(EBRT) and brachytherapy to the rectum and bladder for 0.1cc,1cc and 2cc and compare the outcome to international findings. Methods. 57 patients that completed definitive radiotherapy for cervical cancer were retrospectively reviewed. All patients received EBRT 50Gy in 2Gy daily fractions with brachytherapy 4-5 doses. The dose normalised to the rectum point receiving the highest dose. The combined dose of EBRT and brachytherapy was converted to bio-equivalent dose in 2Gy fractions (EQD2) for each of the volumes of the rectum and bladder. Results. Mean EQD2 dose to the rectum 0.1cc: 63.8(3.3); 1cc: 60.4(2.2); 2cc: 58.9(1.8). Mean doses to the rectum was lower than described in the literature with no patient receiving more than the dose cutoff for 2cc(70Gy). Mean doses to the bladder 0.1cc: 87.4(18.5); 1cc:75,5(11.9) and 2cc: 71,6(10.0). These doses are also lower as described in the literature however two patients received dose higher that the advised cutoff to 2cc of 90Gy. This could have been avoided for one of the patients if the correct method of dose determination was followed. Conclusion. As expected the current dose prescription method yields safe doses to the rectum. The bladder dose is a concern even though only two patients exceeded the tolerance and it could have been avoided. High variation in the bladder dose among patients suggests an opportunity for dose optimisation techniques. These findings should be correlated with clinical outcomes of toxicity.