A multicentre comparison of the dosimetric impact of inter- and intra-fractional anatomical variations in fractionated cervix cancer brachytherapy

Abstract Background and purpose To compare the dosimetric impact of organ and target variations relative to the applicator for intracavitary brachytherapy by a multicentre analysis with different application techniques and fractionation schemes. Material and methods DVH data from 363 image/contour sets (120 patients, 6 institutions) were included for 1–6 fractions per patient, with imaging intervals ranging from several hours to ∼20 days. Variations between images acquired within one (intra-application) or between consecutive applicator insertions (inter-application) were evaluated. Dose plans based on a reference MR or CT image series were superimposed onto subsequent image sets and D 2 cm 3 for the bladder, rectum and sigmoid and D90 for HR CTV were recorded. Results For the whole sample, the systematic dosimetric variations for all organs at risk, i.e. mean variations of D 2 cm 3 , were found to be minor (