Interfractional variability and reproducibility of accumulated dose in cervical cancer radiotherapy associated with...

Pelvic anatomical variations during radiotherapy for cervical cancer may alter delivered dose distributions, affecting target coverage and organ-at-risk (OAR) sparing. This study evaluated interfractional dose variability and the impact of bladder volume on accumulated dose delivery in patients treated with helical tomotherapy. A retrospective analysis of ten cervical cancer patients treated with helical tomotherapy was performed. Accumulated doses were generated using Accuray PreciseART via deformable registration of planning computed tomography (pCT) and daily MVCT images. Percentage dose deviations between planned and accumulated doses were analyzed using paired t-tests, while differences among three bladder volume groups were evaluated using linear mixed-effects models. Accumulated PTV doses were significantly lower than planned, with the greatest reduction in D₉₅ (-3.36%, p < 0.001). Among OARs, the bowel showed the largest reduction, particularly D_195cc (-5.18%, p < 0.001). Medium and large bladder volumes were associated with greater reductions in bowel D_195cc and D_mean than small volumes, with no clear difference between the medium and large groups. Increasing bladder volume also showed a non-significant trend toward greater PTV dose reduction, while bowel dose deviations gradually decreased during treatment. Interfractional anatomical variation caused measurable deviations in accumulated dose, particularly for PTV D₉₅ and bowel D_195cc. Although medium and large bladder volumes were associated with slightly greater bowel dose reductions than small volumes, the between-group differences were modest, with no significant difference between the medium and large groups. These findings support individualized and reproducible bladder preparation.