Dosimetric Comparison of Fixed and Flexible Geometry ICRT Applicators in Patients Treated for Carcinoma Cervix

In intracavitary radiotherapy (ICRT) for cancer cervix, applicator geometry has the potential to impact the doses to organs at risk (OARs) and the coverage of the target volume. At our centre two Varian made Fletcher-style applicator sets, namely defined (fixed) geometry and flexible geometry, are used for ICRT. In the present work, the two types of applicators were compared dosimetrically as per the recommendations of the International Commission on Radiation Units and Measurements (ICRU-38) while delivering high dose rate brachytherapy. Twenty four patients who underwent ICRT were considered for this study. Radiographic method was used for treatment planning on Abacus planning system. ICRU-38 recommended parameters were estimated and compared. Flexible geometry applicator showed 8.8% and 16% higher bladder and rectum point doses as compared to the fixed geometry one but the difference was statistically not significant. The thickness of the pear-shaped isodose volume was larger for the flexible geometry implant also indicating towards higher doses to OARs. The higher bladder and rectum point doses in the case of flexible applicator will need to be validated by a larger data set.